




























































































































































































































































































































































































































































































































































































































































































Class. TX % oS 
Book_ 


Copyright N° 


COPYRIGHT DEPOSIT. 










» 



MOTOR-CAR 

PRINCIPLES 




MOTOR-CAR 

PRINCIPLES 

THE GASOLINE AUTOMOBILE 


BY 

ROGER B. WHITMAN 

>i 

ATJTHOB OF “GAS-ENGINE PRINCIPLES” 


ILLUSTRATED 



NEW EDITION, COMPLETELY REVISED 


) 

) 


* 


D. APPLETON AND COMPANY 
NEW YORK, LONDON MCMXIII 





Copyright, 1907, 1909, 1913, by 
D. APPLETON AND COMPANY 


Printed in the United States of America 







INTRODUCTION 


The development of the gasoline automo¬ 
bile at home and abroad has produced a 
great variety of designs, good, bad, and in¬ 
different, but the advancement of the industry 
has weeded out the unsatisfactory and im¬ 
proved the good until with few exceptions 
the leading makes show a striking similarity 
in all but details. The advantages of certain 
forms of construction have been recognized, 
and their adoption by the large majority of 
makers has produced what may be called a 
standard type. 

The object of this book is to explain the 
principles that underlie automobile construc¬ 
tion and operation, and to illustrate the 
movements and mechanical combinations 
adopted in present-day practice. It is not 
the intention to explain the exact details of 
construction of the different cars, and the il¬ 
lustrations have been prepared with the sole 


v 


VI 


INTRODUCTION 


object of making the principles clear, for 
with an understanding of these there should 
be no difficulty in comprehending any par¬ 
ticular application of them. 

The advantages of magneto ignition for in¬ 
ternal combustion engines are so obvious that 
designers and inventors have directed their 
attention to the perfection of apparatus that 
will improve present methods. The number 
of systems proposed for the purpose is very 
large in comparison with the number ac¬ 
cepted by automobile manufacturers, and as 
in a work of this size it would be impossible 
to describe the many methods for the appli¬ 
cation of the magneto that are on the mar¬ 
ket, attention has been given only to those 
that are in actual, every-day use. 

The lubrication table on pages 326 and 
327, which was prepared by Mr. T. D. Han- 
auer, is reproduced through the courtesy of 
the Scientific American. 


Flushing, N. Y. 


R. B. W. 


CONTENTS 


CHAPTER I 

GASOLINE-ENGINE PRINCIPLES 

PAGES 

Properties of gases—Steam-engine principles—Gas¬ 
oline-engine principles—Combustion and explo¬ 
sion—Events of cycle—Four-cycle and two- 
cycle engines—Strokes of cycle—Fly wheel— 
Valves—Inlet stroke—Inlet valve closing— 
Compression-combustion stroke — Advantages 
of compression—Instant of ignition—Advanc¬ 
ing and retarding ignition—Limit of compres¬ 
sion—Power stroke—Heat losses—Opening of 
exhaust valve—Exhaust stroke—Clearance— 
Back pressure—Steam and gasoline engines 
compared—Gasoline-engine power .... 1~21 

CHAPTER II 

ENGINE PARTS 

Crank shaft—Crank-shaft bearings—Relative posi¬ 
tion of cranks—Connecting rod—Wrist pin— 
Piston and piston rings—Automatically and 
mechanically operated valves—Cams and cam 
shaft—Secondary shaft — Two-to-one-gears— 
Chain-driven cam shaft—Valve-lifter rod— 
Valve locations—Sleeve valves—Muffler—En- 

vii 





• • • 


CONTENTS 


Vlll 

PAGES 

gine cooling—Cooling by water—Pumps—Radi¬ 
ators—Pressure and gravity systems—Cooling 
by air—Lubrication.22~47 


CHAPTER III 

ENGINE BALANCE 

Vibrations of engine—One-cylinder engine—Hori¬ 
zontal double-opposed—Two-cylinder vertical— 
Four-cylinder—Firing order—Balance of three- 
and six-cylinder engines—Comparison of en¬ 
gine types.48 _ 57 


CHAPTER IV 

TWO-CYCLE ENGINES 

Principle—Construction—Ports—Cycle — Action— 

Advantages and disadvantages.58 - 61 


CHAPTER V 

CARBURETION AND GASOLINE FEEDS 

Carburetion—Carburetor—Carburetor parts — Car¬ 
buretor action—Necessity for auxiliary air— 
Auxiliary air inlet—Automatic and mechani¬ 
cally controlled air inlet—Carburetors with side 
and central mixing chambers—Mechanically 
controlled carburetor—Surface carburetors— 
Gravity feed—Pressure feed—Check and relief 
valve.62~85 





CONTENTS 


IX 


CHAPTER VI 

IGNITION PRINCIPLES 

PAGES 

Theory of ignition—Heat losses—Effect of engine 
speed on ignition—Advance and retard—Incor¬ 
rect advance—Fixed ignition—Jump-spark ig¬ 
nition—Parts of the system—Electricity—Cur¬ 
rent—Flow caused by pressure—Generator 
terminals—Positive and negative—Circuit— 
Measurements — Magnetism — Magnetism from 
electricity—Electricity from magnetism—In¬ 
duction . 86~106 


CHAPTER YII 

MAGNETO PRINCIPLES 

Armature—Flow of magnetism—Production of cur¬ 
rent—Extended pole shoes—Magneto setting— 
Speed—Distributor—Circuit breaker—Ground 
connection—Magneto circuit—Advance and re¬ 
tard—Stopping the ignition—Magneto classes 

107-124 


CHAPTER VIII 

TRUE HIGH-TENSION MAGNETOS 

Primary and secondary windings—Circuit—Ac¬ 
tion—Bosch magneto principle—Bosch circuit 
breaker—Construction—Safety spark gap— 
Bosch magneto types—Two-spark ignition— 
Two-spark magneto circuit.125“146 







X 


CONTENTS 


CHAPTER IX 

TRANSFORMER MAGNETOS 

PAGES 

Principle—Induction coil—Magneto circuit—Split- 

dorf magneto—Remy magneto .... 147“161 

CHAPTER X 

BATTERY IGNITION SYSTEMS 

Dry cells—Connections—Storage cells—Timer— 
Bosch battery system—Effect of vibrator 
sparks—Vibrator—Bosch coil—Vibrator coil— 
Vibrator coil system—Two and four-cylinder 
wiring—Master vibrator system—Timer-dis¬ 
tributor system—Delco system—Atwater Kent 
system .162~185 


CHAPTER XI 

COMBINED MAGNETO AND BATTERY SYSTEMS 

Bosch two-independent system—Bosch dual sys¬ 
tem—Splitdorf dual system—Remy dual sys¬ 
tem—Bosch duplex system.186 _ 202 

CHAPTER XII 

SPARK PLUGS, CABLES, TERMINALS, AND COUPLINGS 

Spark-plug parts—Insulator—Electrodes — Gap— 
Spark-plug location—High and low tension 
cables—Static charge — Terminals — Coupling 

203-215 





CONTENTS 


xi 


CHAPTER XIII 

TRANSMISSION 

PAGES 

Transmission parts—Clutches—Friction-cone clutch 
—Reversed friction-cone clutch—Multiple disk 
clutch—Internal expanding* clutch—Change- 
speed mechanisms—Sliding gear: progressive 
and selective types—Use of clutch in changing 
gear .216-239 


CHAPTER XIV 
transmission—( Continued ) 

Planetary type of change-speed mechanism—Indi¬ 
vidual clutch—Friction type—Final drive— 
Turning the direction of the power—Bevel gears 
—Single-chain drive—Propeller-shaft drive— 
Universal joints—Live axle—Floating axle— 
Torsion rod—Double-chain drive—Jack shaft— 
Differential—Bevel-gear differential—Spur-gear 
differential—Driving-gear ratios .... 240“267 

CHAPTER XV 

RUNNING GEAR 

Steering—Front axle—Steering knuckles and arms 
—Drag link—Steering principles—Steering 

mechanisms—Brakes: contracting and expand¬ 
ing—Brakes: single- and double-acting—Run¬ 
ning brake—Emergency brake—Engine as a 
brake—Brake equalizer—Tires—Tire construe- 




CONTENTS 

PAGES 

tion—Tire inflation—Skidding—Antiskid de¬ 
vices — Springs — Shock absorbers — Distance 
rods . 268 - 288 


CHAPTER XVI 

MAINTENANCE AND CONSTRUCTION 

inspection—Washing the car—Tires—Care of the 
engine—Care of the chains—Valve grinding— 

Care of the steeling mechanism—Care of the 
springs—Adjusting the vibrators—Adjusting 
the carburetor—Setting the valves—Truing the 
wheels..> . .. 289~310 


CHAPTER XVII 

CAUSES OP TROUBLE 

Pressure gasoline feed—Gravity gasoline feed— 
Carburetor—Magneto—Dry cells—Storage cells 
—Vibrator coil—Spark plugs—Cables—Switch 
—Timer—Compression.311~319 

CHAPTER XVIII 

EFFECTS OF TROUBLE 

Engine will not start—Engine starts, but will not 
continue running—Explosions stop abruptly— 
Explosions weaken and stop—Steady miss in 
one cylinder—Occasional miss in one cylinder 
—Occasional miss in all cylinders—Engine does 
not develop full power—Engine overheats— 
“Popping” in carburetor—Knocks and pounds 
—Hissing—Engine kicks back on starting— 








CONTENTS 


xm 


PAGES 

Engine will not stop—Muffler explosions — 
Black smoke at exhaust—White or blue smoke 
at exhaust. 320~324 


Lubrication Table 
Testing Chart . 
Index. 


. . . 326 and 327 
between 328 and 329 
.329 








LIST OF ILLUSTRATIONS 


na * PAGE 

1. External and Internal Combustion . 4 

2. Gasoline Engine Cycle. 8 

3. Gasoline Engine in Section .... 23 

4. Crank Shafts.24 

5. One-throw Crank Shaft.25 

6. Connecting Rod.25 

7. Piston and Piston in Section ... 26 

8. Piston Rings.27 

9. Conical Valve Seat.27 

10. Automatic Inlet Valve in Cage . . 27 

11. Cam Action.30 

12. Chain Drive for Cam Shafts ... 32 

13. Seven Arrangements of Valves . . 33 

14. Sleeve Valve Engine.35 

15. Action of Sleeve Valve Engine ... 37 

16. Thermo-syphon System of Water 

Cooling.39 

17. Types of Pumps.41 

18. Radiator Constructions.42 

19. Radiator and Fan.42 

20. Force System of Water Cooling . . 43 

21. Engine Arrangements Showing Order 

of Firing.52 


xv 














xvi LIST OF ILLUSTRATIONS 

FIG. PAGE 

22. Two-Cycle Engine.59 

23. Carburetor Principles.65 

24. Compensating Carburetor, Side-Float 

Chamber .69 

25. Compensating Carburetor, Concentric 

Float Chamber.70 

26. Mechanically Controlled Carburetor . 74 

27. Types of Float Valves.77 

28. Types of Auxiliary Air Inlets ... 79 

29. Gravity Gasoline Feed.82 

30. Pressure Gasoline Feed.82 

31. Check and Relief Valve.84 

32. Principle of Current Flow .... 96 

33. Electric Circuit.97 

34. Magnetism from Electricity .... 100 

35. Magnetizing a Piece of Iron . . . 101 

36. Magnetizing Iron by Electricity . . 102 

37. Electricity from Magnetism .... 103 

38. Armature.108 

39. Flow of Magnetism in Armature . . 109 

40. Production of Current in Magneto . Ill 

41. Extended Pole Shoes of Bosch Mag¬ 

netos .114 

42. Distributors for One, Two, Four and 

Six Cylinders.118 

43. Principle of Spark Advance .... 121 

44. Principle of True High Tension Mag- 


45. Bosch Magneto, Type DU, End View 129 

46. Bosch Magneto, Type DU .... 131 














LIST OF ILLUSTRATIONS 

no. 

47. Bosch Circuit Breaker. 

48. Bosch Magneto, Types D and DR, 

End View. 

49. Bosch Magneto, Types D and DR . . 

50. Bosch Magneto, Type ZR. 

51. Cable Connection of Type ZR . . . 

52. Magneto Connections. 

53. Effect of 2-Spark Ignition . . . . 

54. 2-Spark Magneto Connections . . . 

55. Principle of Splitdorf Magneto . . . 

56. Splitdorf Magneto Ignition System . 

57. Principle of Remy Magneto . . . . 

58. Inductor of Remy Magneto . . . . 

59. Remy Magneto Ignition System . . 

60. Remy Magneto Type RD. 

61. Section of Dry Cell. 

62. Cells Connected in Series . . . . 

63. Cells Connected in Series-multiple . 

64. Action of Bosch Timer-distributor . 

65. Bosch Timer-distributor. 

66. Principle of Vibrator. 

67. Bosch Coil. 

68. Principle of Battery Ignition System 

69. Connections of Two-cylinder Battery 

System. 

70. Connections of Four-cylinder Battery 

System. 

71. Vibrator Coil and Engine . . . . 

72. Master Vibrator Battery System . . 

73. Timer-distributor with Vibrator Coil 


xvii 

PAGE 

132 

135 

137 

139 

140 

141 

143 

144 
150 
154 

156 

157 
159 
161 
163 
165 
167 

170 

171 

172 

174 

175 

177 

178 
180 
182 
184 








xviii LIST OF ILLUSTRATIONS 

PIQ. PAGE 

74. Connections of Bosch 2-Independent 

System.187 

75. Bosch Dual Magneto.188 

76. Connections of Bosch Dual System 190 

77. Bosch Dual Coil.192 

78. Connections of Bosch 2-Spark Dual 

System.192 

79. Principle of Splitdorf Dual System . 194 

80. Principle of Remy Dual System . . 196 

81. Principle of Bosch Duplex System . 197 

82. Connections of Bosch Duplex System 201 

83. Spark Plug.204 

84. Correct Location of Spark Plug . . 207 

85. Pocketed Spark Plug.208 

86. Extended Spark Plug.209 

87. Correct Location of Spark Plug . . 210 

88. Friction Cone Clutches.220 

89. Multiple Disk Clutch.222 

90. Sliding Gear, Progressive Type . . 227 

91. Selective Type .233 

92. Action of Speed Control Lever . . . 236 

93. Planetary Type.241 

94. Propeller and Single Chain Drives . 248 

95. Typical Universal Joint.249 

96. Types of Shaft Drives.251 

97. Live Axle, Non-floating Type . . . 253 

98. Live Axle, Floating Type .... 253 

99. Dead Axle with Driving Shaft . . . 255 

100. Torsion Rod.256 

101. Double Side Chain Drive .... 257 















LIST OF ILLUSTRATIONS xix 


no. PAGE 

102. Differentials.260 

103. Drag Link Positions.269 

104. How Vehicles Turn.271 

105. Steering Mechanisms.274 

106. Three Varieties of Brakes .... 277 

107. Springs.286 

108. Distance or Radius Rods.288 








MOTOR CAR PRINCIPLES 


CHAPTER I 


GASOLINE ENGINE PRINCIPLES 


T HE action of a steam, gasoline, or 
liot-air engine depends on the prin¬ 
ciple that when air or other gas is 
heated it expands, and that if it is confined 
in a space that will not permit it to expand, 
in striving to do so it creates pressure 
against all parts of the chamber in which it 
' is contained. The more a gas is heated, the 
more it will expand if it is free to do so, and 
if not free, the greater will be the pressure 
that it will exert in striving to expand. Pres¬ 
sure may thus be generated by heat, and fol¬ 
lowing along similar lines, heat may be pro¬ 
duced by pressure, for when the pressure of 

1 


2 


MOTOR CAR PRINCIPLES 


a gas is increased by compressing it, or forc¬ 
ing it to occupy a smaller space, the gas will 
become heated. The reverse is also true, that 
when a gas is cooled, its volume is reduced, 
which reduces the pressure that it exerts; 
similarly, reducing the pressure by permit¬ 
ting the gas to expand reduces its tempera¬ 
ture. 

To state these principles in another form, 
to create pressure in a gas it must either be 
heated or compressed into a smaller space, 
and to reduce its pressure it must either be 
cooled or permitted to expand. 

The action of a locomotive, the most 
familiar type of steam engine, is no mystery, 
and the production of steam in the boiler, its 
passage to the cylinder, and the application 
of its steady pressure against first one side 
of the piston and then the other, resulting in 
the turning of the driving wheels, are well 
understood. Water being converted into 
steam in the boiler, pressure is created be¬ 
cause of the tendency of the steam to expand, 


GASOLINE ENGINE PRINCIPLES 3 


but the only place in which it may expand 
is the cylinder, where in so doing it moves 
the piston. 

A gasoline engine is similar to a steam en¬ 
gine in that its piston is moved by the pres¬ 
sure exerted by a heated and expanding gas; 
it is different in that the pressure is pro¬ 
duced inside of the cylinder by the combus¬ 
tion of an inflammable mixture of gasoline 
vapor, instead of being generated in a boiler 
away from the cylinder. The heat of the 
combustion creates great pressure, and as 
the piston is the only part that can give be¬ 
fore it, it is moved from one end of the cylin¬ 
der to the other, this motion being utilized 
in the turning of the crank shaft. The com¬ 
bustion, which is so rapid that the generally 
accepted term for it is explosion, can occur 
only after the mixture has been drawn into 
the cylinder, and so prepared that it ignites 
quickly and burns completely, with the ob¬ 
ject of obtaining the greatest possible heat 
from it in the shortest possible time. In or- 



4 


Fig. 1.—Steam Engine (External Combustion) and Gas Engine (Internal Combustion). 






















































































GASOLINE ENGINE PRINCIPLES 5 


der that one explosion may be followed by 
another, the burned and useless products of 
combustion must be expelled to make place 
for a fresh charge of the inflammable mix¬ 
ture. 

These successive events, forming a cycle, 
must be performed as long as the engine 
runs, and the constantly changing pressure in 
the cylinder due to the movement of the pis¬ 
ton allows a fresh charge to enter, prepares 
it, and expels the products of combustion 
after the pressure that they have exerted has 
been utilized. 

While in the great majority of steam en¬ 
gines the steam acts first on one side of the 
piston and then on the other, in an automo¬ 
bile gasoline engine the pressure is exerted 
on only one side, the combustion of the mix¬ 
ture taking place between the piston and the 
closed end, or head, of the cylinder. The 
other end of the cylinder is open, and the pis¬ 
ton slides between the ends, its movement 
from one end to the other, called a stroke, 


6 


MOTOR CAR PRINCIPLES 


corresponding to a half revolution of the 
crank shaft. 

Gasoline engines are divided into two 
classes, according to the number of strokes 
of the piston that are necessary to accom¬ 
plish the cycle; in the most usual type, four 
strokes are necessary, the class being called 
the four-stroke-cycle, or four-cycle, in dis¬ 
tinction to the two-stroke-cycle, or two-cycle, 
in which but two strokes are necessary. 

Of the five events that compose the cycle, 
three (the inlet, during which the fresh mix¬ 
ture enters the cylinder, its compression or 
preparation, and the exhaust of the burned 
gases) are performed by the piston; during 
the power event the piston is moved by the 
pressure resulting from the combustion, 
while the combustion event is due to an out¬ 
side source. In the four-cycle type of engine, 
which is in almost universal use for automo¬ 
biles, the events are considered with refer¬ 
ence to the movement made by the piston 
during which they are performed, and may 


GASOLINE ENGINE PRINCIPLES 7 


be called the inlet, compression-combustion, 
power, and exhaust strokes. In order that 
the engine may continue to run, it is obvious 
that the events must be performed in the cor¬ 
rect order, and that the failure of one will 
affect all the others. 

During the inlet stroke, a charge of fresh 
mixture enters the cylinder as the piston 
makes an outward stroke from the closed 
toward the open end. When the piston makes 
the following inward stroke, the mixture is 
compressed and combustion occurs, the pres¬ 
sure from which drives the piston outward 
on the power stroke. This is followed by an¬ 
other inward stroke, which pushes the 
burned gases out of the cylinder. It will be 
seen that power is developed during only one 
stroke of the four, the other three being re¬ 
quired in the preparation for the following 
power stroke. The movement of the piston 
over these three dead strokes is secured by 
attaching to the crank shaft a heavy fly 
wheel, the momentum of which, acquired 


SUCTION STROKE 




POWER STROKE 



COMPRESSION STROKE 



EAR RUST STROKE 


Fig. 2.—Gasoline Engine Cycle. 

8 





























GASOLINE ENGINE PRINCIPLES 9 

during the power stroke, keeps the crank 
shaft revolving and the piston in motion 
while the events are performed. 

The space between the piston and cylinder 
head in which the combustion occurs is called 
the combustion space, and the inlet and ex¬ 
haust valves open into it, the first being that 
by which the fresh mixture enters, and the 
second that by which the products of com¬ 
bustion escape. The device for igniting the 
mixture projects into the combustion space, 
and the means of ignition in universal use 
for automobile engines is an electric spark. 

INLET STROKE 

During the stroke (Fig. 2), the piston is 
moved outward by the crank shaft, which is 
revolved either by hand or by the momentum 
of the fly wheel. This movement increases 
the size of the combustion space, thereby re¬ 
ducing the pressure in it, and the higher pres¬ 
sure of the atmosphere outside of the cylin¬ 
der will force fresh mixture into the combus- 


10 


MOTOR CAR PRINCIPLES 


tion space, the inlet valve being open to ad¬ 
mit it. If the piston moves slowly, the mix¬ 
ture will be able to enter fast enough to keep 
the pressure in the combustion space equal 
to that outside, but at the high speed at 
which a gasoline engine is run the piston will 
reach the end of its stroke before a complete 
charge has had time to enter, so that the pres¬ 
sure in the combustion space will still be be¬ 
low that of the atmosphere. If the inlet valve 
closed at this point so that no more mixture 
could enter, the combustion of the partial 
charge would result in a lower pressure than 
would be possible with a full charge; the 
inlet valve should therefore remain open un¬ 
til the piston reaches the point of its next 
inward stroke at which the pressure in the 
cylinder equals that outside. 

COMPRESSION-COMBUSTION STROKE 

The compression and the combustion of the 
charge occur during the next inward stroke 
of the piston. 


GASOLINE ENGINE PRINCIPLES 11 


The period between the bringing together 
of the liquid gasoline and air and its admis¬ 
sion to the cylinder is too brief to secure per¬ 
fect combination, and the mixture that re¬ 
sults is not satisfactory. A portion of the 
air will not have been able to come into con¬ 
tact with the gasoline, and much of the liquid 
will not have been vaporized; what passes 
into the cylinder consists of pure air, liquid 
gasoline, and a more or less perfect mixture 
of the two. The combustion of this would be 
slow and incomplete, resulting in loss of 
power and waste of fuel. In order to render 
the mixture more perfect, advantage is taken 
of the heat that is produced by compression; 
the inward stroke of the piston raises the 
temperature of the mixture by compressing 
it, the heat rendering the gasoline more vola¬ 
tile, and the compression forcing it into com¬ 
bination with the air. Even this does not 
result in the formation of a perfect mixture, 
for the period is too short to effect it. The 
failure of an engine to deliver full power 


12 


MOTOR CAR PRINCIPLES 


may often be traced to this condition, for the 
air and gasoline vapor, instead of being 
thoroughly combined and mixed, will be in 
layers, so to speak, and the combustion will 
be slow and uneven. Future development of 
the internal combustion engine will no doubt 
eradicate this, to the increase of efficiency 
and economy. 

The charge of inflammable mixture can 
produce a certain amount of heat, and the 
more rapidly and completely this heat is ob¬ 
tained, the greater and more sudden will be 
the rise in pressure. The pressure will be 
greater when the mixture is contained in a 
small space than when in a large, and as the 
combustion space is smallest when the piston 
is at its inmost point, the greatest pressure 
will be obtained if combustion is complete at 
this point. If the combustion of the mixture 
were instantaneous, it should be ignited at 
this point; but even though very rapid, it 
nevertheless burns slowly enough to make it 
necessary to ignite it sufficiently before the 


GASOLINE ENGINE PRINCIPLES 13 

end of the stroke to have the combustion 
complete as the piston comes into position 
to move outward. The instant at which the 
mixture must be ignited in order to produce 
this result depends on the speed of the pis¬ 
ton, for the interval between the ignition of 
a good mixture and its complete combustion 
does not vary to any great extent. When the 
piston is moving slowly, the mixture may be 
ignited toward the end of the compression 
stroke, for there will be sufficient time for 
complete combustion by the time the stroke 
is ended; but when moving at high speed, 
ignition must occur much earlier in the 
stroke, as otherwise the piston will have com¬ 
pleted the compression stroke and begun to 
move outward on the power stroke before 
the mixture is entirely burned. The instant 
at which ignition occurs also depends on the 
mixture that is used, for its quality and 
proper combination make a difference in the 
rapidity with which it burns. The better the 
quality of the mixture, the faster and more 


14 


MOTOR CAR PRINCIPLES 


completely it will burn, and ignition may oc¬ 
cur later in the stroke than would be possible 
with a mixture of poor quality. As the mix¬ 
ture is ignited by the passing of an electric 
spark in the combustion space, the difference 
in the instant at which it occurs may be se¬ 
cured by permitting the spark to pass earlier 
or later, and this is under the control of the 
driver. 

When ignition occurs early in the compres¬ 
sion stroke, the spark is said to be advanced, 
in distinction to a retarded spark, which 
passes when the compression stroke is more 
nearly complete. 

If the spark is advanced too much, com¬ 
bustion will be complete before the piston 
has reached the end of the compression 
stroke, and it will be necessary to force it to 
the end of the stroke against the pressure 
by the momentum of the fly wheel, in order 
that it may get into position to move out¬ 
ward on the power stroke. In such a case, 
the momentum may not be sufficient to over- 




GASOLINE ENGINE PRINCIPLES 15 


come the pressure, and the piston will be 
brought to a stop. A retarded spark results 
in the combustion of the mixture being com¬ 
pleted after the piston has begun to move 
outward on the power stroke, and the pres¬ 
sure will then be reduced because it is ex¬ 
erted in a larger space, the piston conse¬ 
quently being moved with less force; if the 
spark is still further retarded, the combus¬ 
tion will not be complete by the time the ex¬ 
haust begins, and the heat from only a por¬ 
tion of the mixture will be utilized, because 
it will still be burning as it is forced out of 
the cylinder. 

The position at which the spark occurs is 
one of the means by which the speed of the 
engine is controlled, for the low pressure that 
results from a retarded spark moves the pis¬ 
ton at low speed, while the greater pressure 
from an advanced spark drives the piston 
outward with more force and higher velocity. 

While high compression of the charge im¬ 
proves its quality, and results in combus- 


16 


MOTOR CAR PRINCIPLES 


tion being more rapid and complete, it has 
limits, and if carried too far the heat gen¬ 
erated by the compression will be sufficient 
to ignite the mixture. This would have a 
bad effect on the operation of the engine, for 
the pressure would then be produced at the 
wrong point of the stroke, retarding instead 
of assisting the revolution of the crank shaft. 
Modern practice has shown that in engines 
that are maintained at a proper temperature 
the best results are obtained by compressing 
the mixture to from sixty to eighty pounds 
to the square inch; there are instances in 
which a higher compression is obtained, but 
the liability to ignite the mixture prema¬ 
turely makes it undesirable. 

POWER STROKE 

« / 

The increasing size of the combustion 
chamber as the piston moves outward on the 
power stroke permits the gases to expand, 
and in doing so the temperature will fall, the 
pressure decreasing in consequence. A fur- 


GASOLINE ENGINE PRINCIPLES 17 


ther decrease in pressure is caused by the hot 
gases being in contact with the metal cylin¬ 
der and piston, which absorb heat. The more 
slowly the engine runs, the longer the gases 
will be in contact with the cylinder walls, 
and the more opportunity there will be for 
loss of heat from this cause; at higher 
speeds, there will be less time for heat to be 
absorbed by the cylinder walls, and more will 
be utilized in expanding the gases and pro¬ 
ducing work. 

Even at the outmost position of the piston, 
the combustion space will not be large 
enough to permit the gases to expand until 
their pressure has dropped to that of the 
atmosphere, so that they will still be exerting 
pressure. By opening the exhaust valve, the 
gases will have an outlet for expansion, and 
will begin to rush out. While the pressure 
might be utilized against the piston to the 
end of the power stroke, it has been found 
that better results are obtained by opening 
the exhaust valve before the piston reaches 


18 MOTOR CAR PRINCIPLES 


the end of the power stroke. There is then 
a higher pressure forcing the gases out than 
there would be later in the stroke, and the 
greater quantity of gases that escapes leaves 
less to be expelled during the exhaust stroke. 

EXHAUST STROKE 

The inward movement of the piston pushes 
out of the open exhaust valve the gases that 
have not escaped through their desire to ex¬ 
pand. The exhaust valve remains open for 
the entire stroke, but when the engine is run¬ 
ning at high speed the piston moves so rap¬ 
idly that the gases cannot escape fast enough 
to prevent their being slightly compressed. 
When the piston is at its inmost point, the 
gases are still flowing through the valve be¬ 
cause of this slight compression, and if the 
valve closed, a portion would be retained. 
The best results come from the closing of the 
exhaust valve not at the end of the exhaust 
stroke, but a short time after the piston has 
begun to move outward again, during which 


GASOLINE ENGINE PRINCIPLES 19 


period the compression forces the gases out. 
The exhaust valve closes at the point when 
the slight compression has been reduced to 
the pressure of the atmosphere by the escape 
of the gases and the enlargement of the com¬ 
bustion space. 

If the piston completely filled the combus¬ 
tion space when at its inmost point, all of 
the burned gases would be expelled, but the 
necessity for leaving a space in which com¬ 
bustion may take place renders this impos¬ 
sible, and a small portion of the burned 
gases therefore remains in the cylinder. The 
space between the cylinder head and the pis¬ 
ton when at its inmost point, called the 
clearance, should be as small as possible, in 
order that the amount of these gases remain¬ 
ing in the cylinder may not be sufficient to 
contaminate the fresh charge and weaken the 
pressure of its combustion. 

The passages through which the burned 
gases are led away from the cylinder must be 
large and free from obstructions, for if a free 


20 


MOTOR CAR PRINCIPLES 


flow is not permitted back pressure will be 
set up, which will prevent the largest possi¬ 
ble amount of gases from escaping, and leave 
a greater portion to contaminate the fresh 
charge. 

The power that a gasoline engine is capa¬ 
ble of developing depends on the size of the 
cylinder, the pressure acting on the piston, 
and the speed at which it operates. A steam 
engine, which obtains its pressure from a 
boiler, can do work as soon as the steam is 
turned into the cylinder, but a gasoline en¬ 
gine must be running before it can be called 
on to deliver power. Because of the cycle of 
events on which its operation depends, the 
piston must be forced to perform the inlet 
and compression strokes before pressure can 
be developed, and it is necessary to revolve 
the crank shaft by outside means until a 
charge of mixture has been taken into the 
cylinder, compressed, and ignited, when the 
engine begins to work by the pressure from 
the combustion, and takes up its cycle. Not 


GASOLINE ENGINE PRINCIPLES 21 

until this lias been done can it be called on 
to do work. 

A steam engine can be made to deliver 
more power than it is built for by increasing 
the pressure acting against its piston, and 
the full pressure of the boiler can be utilized 
when extra work is necessary. The power 
developed by a gasoline engine being greatly 
dependent on its speed, and there being no 
reserve by which greater power can be de¬ 
veloped in emergencies, it is necessary for an 
engine of this type to be perfectly adapted 
to the work that is desired of it. At ex¬ 
cessive speeds the piston acquires great mo¬ 
mentum, which must be overcome at each 
end of a stroke by the crank shaft, and while 
a speed above normal may be attained, it 
results in the quick destruction of the bear¬ 
ings and the severe straining of the engine. 
The best results in efficiency and long life 
accompany the running of the engine at the 
slowest speed possible for the development 
of the required power. 


CHAPTER II 


ENGINE PARTS 


HE sudden and powerful outward 


T 


movements of the piston under the 
pressure from the combustion are 


transmitted to a crank shaft, which must be 
of great strength in order to resist the heavy 
strains under which it operates. It is made 
of the best steel available for the purpose, 
and has as many cranks as the engine has 
cylinders. The cranks are generally made in 
one piece with the shaft for the sake of 
strength, and for stillness there are as many 
bearings as possible. The number of bear¬ 
ings for the crank shaft of an engine with 
four or more cylinders depends on the ar¬ 
rangement of the cylinders. If the cylinders 
are evenly spaced, there will be room for a 
bearing between each pair of cranks, so that 
a four-cylinder engine will have five bear- 


22 



23 









































































24 


MOTOR CAR PRINCIPLES 


ings, one at eacli end, the. other three being 
between the cranks. If the cylinders are in 
pairs, there will not be room between the 
cranks of a pair for a bearing, the only 
space for it being between the pairs; a four- 
cylinder engine built in this way will thus 
have but three bearings, one at each end 
and one in the center. Crank shafts are 

described by t h e i r 
bearings as three, 
five, etc., point 
crank shafts. 




Fig. 4.—A, Two-throw Crank Shaft; B, Four-throw 

Crank Shaft. 


The relative positions of the cranks of a 
crank shaft are expressed in degrees of a 
circle; if, for instance, the cranks project 
from opposite sides of the shaft so that they 

























































ENGINE PARTS 


25 


are a half revolution apart, it is called a 
180-degree crank shaft. 

The outer ends of the crank arms, which 
correspond to the cranks of a bicycle, sup- 


ri-n/zr Ft 
MAfrnrs 


t sCQriKSCIlNG BOO 



Fig. 5.—One-throw Crank 
Shaft. 

port the crank pin, which may be likened to 
the pedal, and to this the large end of the 
connecting rod is attached, the small end 
being connected to the piston. The connect¬ 
ing rod must be of great strength, tough but 
not brittle, and is made of steel or bronze. 

The piston is a trifle smaller than the bore 
of the cylinder, and its length is usually 































26 


MOTOR CAR PRINCIPLES 


greater than its diameter. It is hollow, with 
one end closed, the closed end being that 
against which the pressure is exerted. A 
wrist pin passes through it, and through the 
small end of the connecting rod, to enable the 




Fig. 7.—A, Piston; B, Piston in Section. 


latter to swing from side to side in follow¬ 
ing the turning of the crank shaft. A tight 
joint is maintained between it and the cylin¬ 
der walls by cast-iron piston rings, which are 
of square or rectangular cross-section, split 
so that they may spring open, and fitted into 
grooves cut around the piston. They are of 
such shape that their tendency to expand 
keeps them pressed against the cylinder 











































ENGINE PARTS 


27 


walls, but being split, their elasticity pre¬ 
vents their binding; they tit the grooves 
snugly, and while they may 
move freely in them, they hold 
the pressure from escaping. 

The number of rings varies 
with the design of the engine, Fig. 8—Piston 
but the most usual arrange¬ 
ment is three to a piston, placed around the 



upper end. 

The cylinder should be of the highest 
grade of cast iron, with the smoothest pos- 



Fig. 9.—Conical Fig. 10.—Automatic 

Valve Seat. Inlet Valve in 

Cage. 


The valve openings, or seats, are circular, 
and are usually made slightly funnel shaped, 




















28 


MOTOR CAR PRINCIPLES 


the disks that cover them being slightly con¬ 
ical to fit. The large end of the funnel is 
toward the combustion space, so that when 
the disk is lifted from its seat it moves in¬ 
ward. Valves are held against their seats 
by coil springs that surround the valve 
stems, which are rods extending from the 
center of the disks, and there are two 
methods by which they are opened. In an 
automatic valve, the spring that holds the 
disk against its seat is weak, and the higher 
pressure outside of the cylinder during the 
suction stroke draws the disk away from its 
seat against the pressure of the spring. The 
valve remains open until the pressure in the 
combustion space is about equal to that out¬ 
side, when the spring draws the disk back to 
its seat, to which it is held as long as the 
pressure inside is higher than that of the 
atmosphere. This arrangement is only pos¬ 
sible for inlet valves, and is now rarely used, 
for exhaust valves, as well as inlet valves, 
are mechanically operated; that is, they are 


ENGINE PARTS 


29 


opened and held open by a mechanism driven 
by the crank shaft, in the form of a cam. A 
cam can best be described as a “ wheel with 
a lnimp on it,” or, in other words, it is a 
piece of metal mounted on a shaft, cylin¬ 
drical in form except for one portion, which 
projects farther from the shaft than the rest. 
The cam revolves with the shaft, and the 
projection, called the nose, will displace any¬ 
thing resting against it. The illustration 
shows a cam in three positions of its revolu¬ 
tion, with the end of a valve stem resting 
against it—the roller being attached to the 
stem to reduce the friction. The valve stem 
is held in guides, so that the only movement 
it may have is up and down; when the cam 
revolves, the nose lifts the stem and opens 
the valve, holds it open as long as the flat 
end of the cam is under the steam, and when 
the nose passes from under, the valve is 
drawn to its seat by the spring. 

The moment at which an automatic valve 
opens is governed partly by the tension of 


30 


MOTOR CAR PRINCIPLES 


its spring; if it is too strong, greater pres¬ 
sure will be required to open it, and it will 
close sooner than if the tension is light. Ac¬ 
curate adjustment of this spring is necessary 
in order that the charge may enter the com- 



Fig. 11.—Cam Action. 


bustion space without delay, and continue to 
enter as long as possible. The opening and 
closing of mechanically operated valves de¬ 
pend on the shape of the cam, and not being 
affected by the more or less uncertain action 
of a spring, they are more positive in action. 

The cam shaft on which the cam is 
mounted is driven by the crank shaft, but as 
the valve opens but once during two revolu¬ 
tions, the cam shaft revolves at half speed, 
making one revolution while the crank shaft 






ENGINE PARTS 31 

makes two. This is done by means of 

gears. 

If two gears running together, or in mesh, 
have the same number of teeth, they will 
make the same number of revolutions, but if 
one has twice as many teeth as the other, the 
smaller will revolve twice while the larger 
revolves once. As the cam shaft must re¬ 
volve but once while the crank shaft revolves 
twice, its gear must have twice the number 
of teeth as the gear on the crank shaft. The 
cam shaft is also called the secondary, or 
half-time shaft, and the gears that drive it 
the two-to-one gears. 

It is quite usual for the cam shaft to be 
driven by a chain instead of by gears, and 
Figure 12 shows two arrangements of chain- 
driven cam shafts. The chain drive has the 
advantage of being noiseless. 

In some designs of engines, the nose of the 
cam bears directly against the valve stem, 
but it is more usual to place a valve-lifter 
rod, or push rod, between them, the cam act- 


32 


MOTOR CAR PRINCIPLES 


ing on the rod and lifting it, and that in turn 
lifting the valve stem. When the nose of the 
cam is not acting on the stem or rod, there 
must be a small space between them, for if 
the stem or rod rests firmly against the cam 



Fig. 12.—Chain Drive for Cam Shafts. 


at all times, the valve disk might be pre¬ 
vented from seating firmly. The space is 
left between the stem and lifter rod, the 
spring acting only on the stem. 

The valves may open into the cylinder in a 
variety of ways; both may be in one pocket, 
or one may be in a pocket and the other in 
the head, or each in a separate pocket, or 
both in the head. Seven arrangements of the 












ENGINE PARTS 33 


valves are shown in Figure 13. All of these 
are in common use, but the most popular is 
probably that shown in the third sketch, in 
which the valves are side by side in a single 







Fig. 13.—Seven Arrangements of Valves. 


pocket; a cylinder of this type is called an 
L-head. When the valves are in separate 
pockets on opposite sides, as shown in the 
first sketch, the cylinder is called a T-head. 

When valves are set in the cylinder head, 
as shown in the second, fourth, fifth, sixth 
and seventh sketches, they are operated by 
means of rocker arms, or else the cam shaft 































34 


MOTOR CAR PRINCIPLES 


is placed above the cylinders instead of be¬ 
low them. 

Valves of the kind described are known as 
poppet valves, and for many years nothing 
else was used. Their operation is satisfac¬ 
tory, but when worn they are inclined to be 
noisy. In order to eliminate noise from this 
source, valves of the sleeve type have been 
produced, and a sleeve valve engine is illus¬ 
trated in Figure 14. It consists of a station¬ 
ary cylinder containing two movable cylin¬ 
ders open at both ends, like pieces of pipe, 
and called the outer sleeve and the inner 
sleeve. These sleeves tit snugly, and are 
arranged to slide up and down in the cylin¬ 
der. Inside of the inner sleeve is the piston, 
which is of the usual construction. 

There are slots or ports cut part way 
around the upper part of the cylinder, one on 
each side, for the inlet and exhaust. Each 
of the sleeves has similar slots, and the ac¬ 
tion of the engine brings the sleeve slots in 
line with the cylinder ports, first on one side 


packing 

rings 


INLET 



CRANK 

SHAFT 


Fig. 14.—Sleeve Valve Engine. 


35 


































































36 


MOTOR CAR PRINCIPLES 


and then on the other. Openings are thus 
provided by which the fresh mixture may 
enter and the burned gases may escape. Dur¬ 
ing the compression and power strokes the 
sleeves cover the ports. 

The cylinder head is so shaped that the 
sleeves may move up into a channel in it, 
and a tight joint is maintained by packing 
rings, which are similar to piston rings. 
Pressure is thus prevented from leaking dur¬ 
ing the compression and power strokes. The 
movement of the sleeves into the channel 
protects the edges of the slots from the 
intense heat developed during the power 
stroke. 

The sleeves are driven by short connecting 
rods operated by eccentrics mounted on a 
shaft that corresponds to the cam shaft of a 
poppet valve engine. 

Figure 15 shows the positions of the 
sleeves during the four strokes of the cycle. 
Each sleeve makes one upward and one 
downward stroke while the piston makes 



37 
























































































38 


MOTOE CAE PEINCIPLES 


four strokes; or, in other words, while the 
crank shaft makes two revolutions. 

The sleeve principle was first used in the 
Knight engine, but it has been applied in a 
number of other designs. 

If after the explosion the burned gases 
were permitted to escape directly into the 
open air from the cylinder, the effect would 
be the same as the firing of a gun, and for 
the same reasons. The pressure in the cylin¬ 
der being higher than that of the atmos¬ 
phere, the sudden expansion of the gases 
would produce a report, and as this would 
be most undesirable for an automobile, pro¬ 
vision is made by which the gases are cooled 
and permitted to expand gradually, so that 
when they reach the open air they are at its 
pressure, or nearly so. This is done in the 
muffler, or silencer, to which the exhaust pipe 
conducts the products of combustion. The 
muffler consists of a series of chambers of 
different sizes, one inside of the other; the 
gases pass from the smaller to the larger, ex- 


ENGINE PARTS 


39 


pending as they go, until from the largest 
they should escape without noise, having lost 
their heat and pressure. 



Fig. 16.—Thermo-siphon System of Water-cooling. 


While the pressure exerted during the 
power stroke depends on the heat of the 
gases, and it is necessary to have the engine 
hot in order that there may be as little loss of 
heat as possible, the temperature must not be 
permitted to rise to the point at which the 
lubricating oil would burn. Lubricating oil 



















































40 


MOTOR CAR PRINCIPLES 


for gasoline engines is made to stand high 
heat, but if heated beyond its limit it will 
burn, and then, besides the loss of its prop¬ 
erty of lubrication, a deposit of carbon, hard 
or gummy, will form, fouling the combustion 
space or piston rings, and interfering with 
the operation of the engine. Overheating 
is prevented either by circulating water 
through channels surrounding the combus¬ 
tion space, or by directing a blast of air 
against it. 

The channels, called water jackets, pro¬ 
vided for the circulation of the water, are 
usually cast with the cylinder, or formed of 
sheet metal. Cool water enters at the bottom 
and escapes at the top, absorbing heat during 
its passage. Of the two systems of keeping 
the water in circulation, the most usual con¬ 
sists of a rotary pump, which forces the 
water through the jackets and then to a 
cooler, or radiator, which is so placed that it 
is exposed to the air currents set up as the 
car moves. In order to cool the water, the 


ENGINE PARTS 


41 


radiator must have a large surface exposed 
to the air, and the water must pass through 
it in small streams. The early types con- 



Fig. 17. — A, Centrifugal Pump; B, Valve Pump; C, Gear 

Pump and Cover. 

sisted of coils of small copper tubing, on 
which were strung disks of copper, the water 
flowing through the tubing, and the disks ab¬ 
sorbing its heat and giving it up to the air, 
but these are being abandoned in favor of 
cellular or honeycomb radiators. These 
















42 MOTOR CAR PRINCIPLES 


types, which are usually placed at the ex¬ 
treme front of the car, are made up of a 



Fig. 18. —Radiator Constructions. A, spiral flange 
(water passes through the tube) ; B, cellular, and C, 
honeycomb (air passes through the tubes; water passes 
through the tubes). 


great number of short lengths of small tub¬ 
ing, in any one of several shapes, placed side 

by side, and held together 
either by plates or by sol¬ 
dering their ends. 

The heated water enters 
at the top of the case in 
which the tubes are con¬ 
tained, and flows to the 
bottom, finding passages 
between the tubes, while the air passes 
through, being assisted by a fan driven by the 
engine. 



Fig. 19. — Radiator 
and Fan. 
















































ENGINE PARTS 


43 


The second system of keeping the water in 
circulation follows the principle that heated 


-£ 



Fig. 20.—Force System of Water-cooling. 


water tends to rise, its place being taken by 
the cooler water that tends to sink. This, 












































































































44 


MOTOR CAR PRINCIPLES 


called the thermo-siphon or gravity system, 
requires all of the parts and connections to be 
large and completely filled with water. The 
water in the jacket rises as it absorbs heat 
from the cylinder walls, and flows out to the 
radiator, which it enters at the top. Its 
place in the jacket is taken by the cooled 
water from the bottom of the radiator, and 
this circulation continues, being more rapid 
as the difference in temperature between the 
heated and cooled water increases. It is nat¬ 
urally not so rapid as circulation that is 
forced by a pump, and more liable to become 
inoperative by the clogging of the pipes, 
jacket, or radiator. 

Of the methods of increasing the surface 
of a cylinder in order to cool it by a blast of 
air, the most usual is to cast it with flanges 
that project from all parts of the combustion 
space. These become heated as the tempera¬ 
ture of the cylinder walls increases, and the 
air that is blown against them carries off the 
heat. Other methods consist of setting pins 


ENGINE PARTS 


45 


or copper strips into the cylinder walls, of 
sncli form that the air current strikes a sur¬ 
face composed of points, by which the heat 
easily passes to the air. Another system con¬ 
sists of surrounding the combustion cham¬ 
ber with a jacket open at the bottom, air 
being drawn through it from the top by a 
powerful blower or by a suction fan. 

Other things that are necessary for suc¬ 
cessful air cooling are large valves by which 
the hot gases may be quickly discharged 
when their period of usefulness is ended, and 
small cylinders rather than large, as the heat 
from small quantities of gases may be car¬ 
ried off more quickly than from large. 

The lubrication of a gasoline engine must 
be carefully looked after, as on its thorough¬ 
ness depends the continued delivery of 
power. The most usual method of lubricat¬ 
ing the piston and cylinder walls is to keep 
the crank case filled with oil to such a point 
that the end of the connecting rod dips into 
it in turning. This spatters the oil to all 


46 MOTOR CAR PRINCIPLES 


parts of the crank case, and a portion is 
caught in a groove cut around the lower end 
of the piston. The inward movement of the 
piston spreads the oil on the cylinder walls, 
and it is distributed around the piston rings, 
so that they move easily in their grooves. 
As the oil is used up, it is replaced from a 
lubricator so that a constant level is main¬ 
tained, and this operates either by gravity, 
or by a small force pump driven by the en¬ 
gine, or by the maintaining of pressure in the 
oil tank. 

Mechanically operated or pressure lubri¬ 
cators supply oil to all parts of the engine, 
and as the quantity passed to each bearing 
is adjustable, a feed may be maintained that 
is exactly suited to the requirements. 

The bearings of an automobile operate un¬ 
der such widely different conditions that one 
kind of lubricant will not be suitable for all. 
The maker of the car has tested the different 
oils, and it is advisable to follow his instruc¬ 
tions on the brand and grade most suitable 


ENGINE PARTS 


47 


for each bearing, rather than to try experi¬ 
ments. The Lubrication Table on pages 326 
and 327 gives the kind and quantity of lubri¬ 
cant most suitable to the work performed by 
each bearing. 


CHAPTER III 


ENGINE BALANCE 

A DRAWBACK to the use of recipro¬ 
cating engines is that the weight of 
the piston and connecting rod in 
sliding first one way and then the other pro¬ 
duces great vibration, and that the crank 
shaft in bringing these parts to a stop at 
each end of the stroke is subjected to violent 
shocks that in time wear it loose in its bear¬ 
ings. With internal-combustion engines this 
vibration, and the shock on the crank shaft, 
are greatly increased by the intensity with 
which the pressure is exerted. 

Engines with one cylinder may be bal¬ 
anced to some extent by the use of counter¬ 
weights attached to the crank shaft, and by 
the use of so heavy a fly wheel that its mo¬ 
mentum produces a comparatively steady 
movement; but a perfect absorption of the 

48 


ENGINE BALANCE 


49 


vibration would require the engine to be run 
at a constant speed, which is not possible 
with those used on automobiles. 

In two-cylinder engines the vibration may 
be reduced by so arranging the parts that the 
pistons slide in opposite directions, the 
weight of one being balanced by that of the 
other. This plan is used in engines of the 
horizontal double-opposed type, which is 
considered to be the most satisfactory for 
low powers. The cylinders are horizontal, 
with their open ends toward each other, the 
crank shaft lying between them. The crank 
shaft is two-throw, 180°; that is, there are 
two pairs of crank arms, projecting from op¬ 
posite sides of the shaft, so that they are 
a half revolution apart. 

Two cylinder engines are also built with 
vertical cylinders, and are of two types, ac¬ 
cording to the construction of the crank 
shaft. In one, the crank shaft is 180°, and 
in the other both pairs of crank arms project 
from the same side of the shaft so that the 


50 


MOTOR CAR PRINCIPLES 


crank pins are in line, this being called a 
360° crank shaft. 

In the 180° type one piston moves up as 
the other moves down, so that they balance, 
but it results in the power strokes occurring 
in both cylinders during one revolution of 
the crank shaft, with no power during the 
revolution that follows. 

To understand the reason for this, the or¬ 
der in which the events of the cycle occur 
must be recalled, and it must be remembered 
that of the four strokes of the piston during 
which they are performed the two outward 
strokes are inlet and power, and the two in¬ 
ward strokes compression and exhaust. If 
the piston of a two-cylinder vertical engine 
(Fig. 21) is moving downward on the power 
stroke, piston No. 2 will be ascending, and 
the only events that can then be performed 
in its cylinder are compression or exhaust. 
If performing compression, it will move un¬ 
der power during the next stroke (the other 
half of the revolution), No. 1 then exhaust- 


ENGINE BALANCE 


51 


ing (Table No. 1). This brings the two 
power strokes in one revolution, and during 
the next revolution there will be no power 
stroke, for No. 1 will be performing suction 
and compression, and No. 2 exhaust and suc¬ 
tion. 

If, as shown in the second table, No. 2 is 
moving upward on exhaust while No. 1 
moves down under power, its previous 
stroke, the first half of the revolution, will 
have been the power stroke, and the same 
condition will exist of two power strokes oc¬ 
curring in the same revolution. 

In either case the balance of the moving 
parts is offset by the irregular production of 
power, which produces bad results in the set¬ 
ting up of strains in the engine, and the un¬ 
even running of the car. 

In two-cylinder vertical engines with 360° 
crank shaft (Fig. 21) the pistons move up 
and down together, which of course results 
in bad balance. In this arrangement, how¬ 
ever, the applications of power may be 



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Fig. 21.—Engine Arrangements Showing Order of Firing. 

52 














































































































































ENGINE BALANCE 


53 


evenly spaced, for as the piston in cylinder 
No. 1 moves downward on the power stroke, 
piston No. 2 moves in the same direction, and 
may make either the inlet or power stroke. 
If it makes the inlet stroke, it must move in¬ 
ward before it can again move outward on 
the power stroke, and there will be an in¬ 
terval of one stroke between the power 
strokes of the two cylinders. To have the 
power strokes in the two cylinders occur to¬ 
gether, as suggested as the alternative, 
would obviously give bad results in the great 
strain imposed on the crank shaft, the 
weight of the fly wheel that would be neces¬ 
sary to carry two pistons through three 
dead strokes, and the jerky running of the 
car. 

The defects of two-cylinder vertical en¬ 
gines with either design of crank shaft out¬ 
weigh any possible advantage of that con¬ 
struction, and the horizontal double-opposed 
type, in evenly occurring power strokes, 
mechanical balance, and simplicity, is in 


54 MOTOR CAR PRINCIPLES 

almost universal use for cars of low 
power. 

A two-cylinder engine does not require so 
heavy a fly wheel as a one-cylinder engine in 
proportion to the power delivered, because 
there is a power stroke every revolution in¬ 
stead of in alternate revolutions, and the 
parts must be carried over only one dead 
stroke instead of three. Similarly, the fly 
wheel of a four-cylinder engine may be still 
lighter, for in that type there are two power 
strokes in every revolution, with no dead 
strokes. At the same time, it is not possible 
to dispense with it entirely, for the pressure 
acting on the piston at the beginning of the 
power stroke falls rapidly as the piston 
moves before it, and the momentum by 
which the fly wheel tends to revolve at a con¬ 
stant speed steadies and smooths what would 
otherwise be a jerky motion. 

The crank shaft of a four-cylinder engine 
is 180°, four-throw, with the two end cranks 
projecting in the opposite direction to that 


ENGINE BALANCE 


55 


of the two inside cranks. This arrangement 
is used in preference to having the cranks 
project alternately; that is, the first and third 
to one side and the second and fourth to the 
other, because of economy in manufacturing, 
and because practice has shown that it re¬ 
sults in less vibration in the running of the 
engine. 

This construction of the crank shaft does 
not permit the power strokes to occur in ro¬ 
tation, cylinder No. 2 following No. 1, and 
then Nos. 3 and 4, for it has been explained 
that when cranks are 180° apart the power 
strokes occur during one revolution, and 
that when 360° apart there is a dead stroke 
between the two power strokes. Cranks 1 
and 2 are 180° apart, as are 3 and 4, and also 
2 and 4, but 2 and 3 are 360°; that is, their 
crank pins are in line, which is also the case 
with 1 and 4. The power stroke in cylinder 
No. 2 may follow that in cylinder No. 1, but 
must be followed by that in cylinder No. 4, 
as that is 180° away from No. 2, and No. 3 


56 


MOTOR CAR PRINCIPLES 


comes last, being 180° from No. 4. The suc¬ 
cession in which the power strokes occur, 
called the firing order, is thus 1, 2, 4, 3, and 
this is arranged for by the setting of the 
valves and the timing of the ignition. 

This firing order was used for the first four- 
cylinder automobile engines, but it has lately 
been suggested that the firing order 1, 3, 4, 2 
shows advantages in the reduction of strains 
and vibration, and it is being adopted. 

Three-cylinder engines are built with 120° 
crank shafts; that is, the cranks are one third 
of a revolution apart, instead of one half of 
a revolution, as is the case with 180° crank 
shafts. This gives three power strokes dur¬ 
ing two revolutions, and results in excellent 
balance. Six-cylinder engines have crank 
shafts of similar construction, and produce 
six power strokes during two revolutions, 
with the best balance that it is possible to 
obtain without an excessive number of cylin¬ 
ders. A power stroke occurs at every 120° 
that the crank shaft revolves, and as each 


ENGINE BALANCE 


57 


power stroke endures for a half revolution, 
or 180°, it follows that one commences when 
the previous one is only two thirds complete. 
This gives a very steady application of 
power, for the crank shaft is at all times 
operated by the driving effect of the combus¬ 
tion strokes, and it is possible to run the en¬ 
gine smoothly at greatly varying speeds by 
control of the position at which the spark 
occurs in the combustion space, and the ad¬ 
mission of a greater or less volume of the 
mixture during the inlet stroke. 


CHAPTER IV 


TWO-CYCLE ENGINE 


T HE two-cycle type of gasoline engine 
differs from the four-cycle type de¬ 
scribed in the foregoing chapters in 
that the five events composing the cycle are 
performed during one revolution of the crank 
shaft, or two strokes of the piston, power 
being developed during every outward 
stroke of the piston instead of alternate out¬ 
ward strokes. 

In order that this result may be attained, 
the construction of the engine is changed, 
and, as will be seen in Figure 22, the crank 
case is utilized as a receiver for the mixture 
before it passes to the combustion space. 
The valves are replaced by ports, which are 
openings into the combustion space that are 
covered and uncovered by the piston as it 
slides in the cylinder. The inlet port is un- 

58 


SPA*K FIMC 


Of PASS FROtt CRAWK CASS TO CBnauST/Ort CHAMBER 



/MDICATES 


FRESH CAS 


V - 0~ <| INDICATE S BORNEO CAS 



Fig. 22.—Two-cycle Engine. 


59 


































































































































60 MOTOR CAR PRINCIPLES 


covered when the piston is at the inmost 
point of its stroke (Fig. 22, A), and then ad¬ 
mits the mixture to the crank case; the 
by-pass port and the exhaust port are uncov¬ 
ered when the piston is at the outmost point 
of its stroke (Fig. 22, B), the former then 
permitting the mixture to pass from the 
crank case to the combustion space, and the 
latter is that through which the burned gases 
escape after combustion has taken place. 

During an inward stroke, the pressure in 
the crank case is reduced as the piston slides 
away from it, and fresh mixture is forced 
into it by the higher atmospheric pressure as 
soon as the inlet port is uncovered. This port 
is covered when the piston makes an out¬ 
ward stroke, and the mixture, not being able 
to escape, is compressed. Its tendency to ex¬ 
pand causes it to flow to the combustion 
space when the by-pass port is uncovered, 
and in entering it strikes a ledge on the pis¬ 
ton so that it is deflected to the top of the 
combustion space instead of being able to 


TWO-CYCLE ENGINE 


61 


shoot across the cylinder and out the open 
exhaust port. The inward stroke of the pis¬ 
ton covers these two ports and compresses 
the mixture, ignition occurring in the regu¬ 
lar manner. The pressure developed by the 
combustion drives the piston outward, and 
as soon as the exhaust port is uncovered 
(which is slightly before the uncovering of 
the by-pass port), the gases, which are still 
expanding, begin to escape, and are further 
expelled by the fresh charge that enters and 
drives them before it. Thus the five events 
of the cycle are performed during an inward 
and an outward stroke of the piston, the 
crank case end of the piston drawing a 
charge of fresh mixture into the crank case 
and forcing it into the combustion space, and 
the combustion chamber end compressing it 
and being acted on by the pressure from the 
combustion. 


CHAPTER V 


CABBURETION AND GASOLINE FEEDS 


P URE gasoline vapor will not burn, and 
in order to render it inflammable it 
must be combined with oxygen. The 
simplest manner of effecting this is to mix 
air with it, and when the correct proportions 
are obtained, the oxygen supplied by the air 
will be sufficient to result in the complete 
combustion of the gasoline vapor, without a 
surplus of either of the ingredients. This 
mixing is called carburetion, the air being 
said to be carbureted. A correct proportion 
of gasoline vapor and air results in rapid 
combustion; an excess of air makes combus¬ 
tion slower, and excess of gasoline vapor pre¬ 
vents the combustion from being complete, a 
residue of carbon remaining. The correct 
proportions of air and gasoline vapor are ob¬ 
tained by the use of a device called a car- 

62 


CARBURETION 


63 

buretor, which is connected to the combus¬ 
tion chamber by the inlet pipe, and in such a 
manner that everything entering the combus¬ 
tion space by the inlet valve must first pass 
through it. 

Liquid gasoline is led to the carburetor 
from the supply tank, and the air enters it 
when the pressure in the combustion space 
is reduced by the jDiston in making the inlet 
stroke. The speed with which the air flows 
through the carburetor depends on the ex¬ 
tent to which the pressure is reduced, and 
the gasoline vapor that is required to form 
a mixture of the correct proportion must be 
maintained in accordance with it. While 
there are various classes of carburetors, prac¬ 
tically all that are used for automobile en¬ 
gines are of the float-feed type; that is, the 
supply of gasoline is maintained by a float, 
just as water tanks are kept filled to a de¬ 
sired depth by a hollow metal ball that floats 
on the liquid and controls the valve by which 
the water enters. 


64 


MOTOR GAR PRINCIPLES 


The principal parts of a float-feed car¬ 
buretor are the float chamber and the mixing 
chamber, the gasoline flowing from the sup¬ 
ply tank to the float chamber, and from there 
to the mixing chamber, where it is combined 
with the air. The gasoline flows out of the 
float chamber through a small pipe, the end 
of which, called the spray nozzle, projects 
into the mixing chamber so that the current 
of air rushes past its tip (Fig. 23). When 
the inlet stroke is not being performed, and 
there is no air passing through the mixing 
chamber, the float in the float chamber keeps 
the gasoline at such a level that it stands just 
below the tip of the spray nozzle. In this 
condition the gasoline in both the float cham¬ 
ber and the spray nozzle is under atmos¬ 
pheric pressure; but when the pressure in 
the combustion space is reduced as the pis¬ 
ton makes the inlet stroke, the pressure in 
the inlet pipe and mixing chamber is also 
reduced, and the gasoline will be forced out 
of the spray nozzle by the higher pressure in 




Fig. 23.—Carburetor Principles. 


65 















































































































66 MOTOR CAR PRINCIPLES 


the float chamber. The passage in the tip of 
the spray nozzle is small, and the gasoline is 
broken up into fine drops as it spurts out, 
and in this condition is partly absorbed by 
the air and partly carried into the cylinder. 
By regulating the amount of gasoline that 
may pass out of the spray nozzle, it may be 
adjusted to the volume of air flowing 
through the mixing chamber, so that any de¬ 
sired proportion may be obtained. 

If the engine were to be run at a constant 
speed, the relative pressures on the gasoline 
in the float chamber and spray nozzle, and 
the quantity of gasoline forced out of the 
spray nozzle, would remain in correct propor¬ 
tion to the volume of air; but as the engine 
of an automobile is run at greatly varying 
speeds, the pressure in the mixing chamber 
is not constant, but varies to correspond. If 
the piston makes fifty inlet strokes a minute, 
the reduction of the pressure in the mixing 
chamber is more gradual than would be the 
case with the piston making two hundred 


CARBUKETION 


67 


inlet strokes a minute. The more rapidly the 
pressure is reduced, the greater will be the 
effect of the unchanging atmospheric pres¬ 
sure in the float chamber, and the more gaso¬ 
line will be forced out of the spray nozzle. 
This will result in the presence of too much 
gasoline in proportion to the air, giving a 
mixture that is too rich. It is therefore nec¬ 
essary to provide an arrangement by which 
the pressure in the mixing chamber will not 
be changed as the speed of the engine varies, 
and this is accomplished by the auxiliary air 
inlet, which is closed when the engine runs 
slowly, but opens to correspond with increas¬ 
ing speed (Fig. 23). The faster the engine 
runs, the more the auxiliary air inlet will 
open, to admit a correspondingly greater 
amount of air to prevent the pressure in the 
mixing chamber from being reduced below 
the point at which the required amount of 
gasoline is forced out of the spray nozzle. 

The most rapid combination of the gaso¬ 
line and air is secured by breaking the gaso- 


68 


MOTOR CAR PRINCIPLES 


line up into fine spray as it leaves the nozzle. 
In order to break the gasoline into fine par¬ 
ticles, the tip of the spray nozzle is made 
with a fine opening, and often forms the seat 
for the gasoline adjusting valve, which is a 
needle-pointed rod that is screwed in or out 
to reduce or enlarge the opening; a further 
breaking up results from the placing of a 
metal cone, or the end of a rod, in such a po¬ 
sition as to be struck by the gasoline as it 
flows out. 

A carburetor with an auxiliary air inlet is 
provided with two points of adjustment, to 
control the flow of gasoline from the float 
chamber to the spray nozzle, and to govern 
the admission of the auxiliary air. The flow 
of gasoline must be just sufficient to carburet 
thoroughly the air passing through the mix¬ 
ing chamber when the engine runs at low 
speed, and the auxiliary air inlet must open 
to correspond with increasing speed, to ad¬ 
mit sufficient air to keep the pressure re¬ 
duced to proper proportions. 


CARBURETION 


69 


The auxiliary air inlet may be operated 
either by the reduced pressure that permits 
the atmospheric pressure to open a valve, or 



IqHj ^mixing; 


AIR \ALVE 
ADJUSTMENT 


„$PRAY* 

NOZZLE. 


FLOAT 

VALVE' 


■STRAINER 


iOUNE INLET 


GASOLINE 

ADJUSTMENT 


EXTRA AIR 


FLOAT 


HAMBER 


MAIN 


MIXTURE 

OUTLET 


F IG> 24.—Compensating Carburetor, Side Float Cham¬ 
ber. 


by the governor of the engine, which opens 
the inlet as the speed increases, and closes it 
on slowing down. The first of these two 
types, called a compensating carburetor, is 
in most general use for automobiles, and is 






































70 


MOTOR CAR PRINCIPLES 


sufficiently satisfactory, but is not as ac¬ 
curate as the mechanically controlled type, 
which acts independently of pressure, and 
exactly according to the speed of the engine. 



a GASOLINE 
ADJUSTMENT 


EXTRA AIR 
VALVE' 


MIXTURE 

outlet 


SPRAY 

NOZZLE 


IfLOAT 
1 VALVE 


Fig. 25.—Compensating Carburetor, Concentric Float 

Chamber. 


Carburetors may be divided into two 
types, according to design: those in which 
the float and mixing chambers are side by 
side, and those in which the mixing chamber 
passes through the center of the float cham¬ 
ber (Figs. 24 and 25). The former is along 






































CARBURETION 71 

the lines of the first forms of float-feed car¬ 
buretors, and the latter is of more recent de¬ 
sign, its object being a more compact device, 
and one that is not affected by a change of 
level when the car is on a hill. Both have 
advantages and disadvantages, and the use 
of one as against the other is optional and a 
matter of opinion. 

The carburetors illustrated are not of any 
particular makes, and are intended to show 
principles rather than construction. 

In carburetors with a side mixing chamber 
the float is usually a metal box, the joints of 
which are as far as possible proof against 
leakage. Guides prevent it from having any 
but an up-and-down motion, and in thus 
moving it controls the gasoline inlet valve by 
a rod attached to it, or by a separate valve 
stem. When the level in the float chamber 
drops as the gasoline runs out of the spray 
nozzle, the float sinks, and the float drops 
from its seat. This admits gasoline from the 
supply tank, and the float in rising on it 


72 


MOTOR CAR PRINCIPLES 


draws the valve to its seat, and shuts off the 
flow. The gasoline adjusting valve is in the 
spray nozzle. The main or initial air inlet 
is in the top, the air entering through the 
upper part of the mixing chamber. The aux¬ 
iliary air inlet is a simple valve, opening in¬ 
ward, and held against its seat by a coil 
spring, the tension of which is adjustable. 
The pressure in the mixing chamber being 
reduced in accordance with the increasing 
speed of the engine, the valve is opened more 
and more as the atmospheric pressure 
against the outer surface of the valve over¬ 
comes the tension of the spring. 

In carburetors with central mixing cham¬ 
ber the float is ring- or horseshoe-shaped, and 
usually made of cork, well varnished to pre¬ 
vent the absorption of the gasoline. The air 
enters at the bottom, passing directly to the 
mixing chamber. The auxiliary air inlet is 
at the top, and is of the arrangement already 
described. The mixture passes out at the 
side, and may be controlled by a throttle, 


CARBUKETION 


73 


which may be a damper arrangement, or 
other device by which the quantity passing 
to the combustion space is at the will of the 
operator. 

The float and mixing chambers of a me¬ 
chanically operated carburetor dre the same 
as in the side-float chamber type, the differ¬ 
ence being in the control of the auxiliary air 
inlet (Fig. 26). This consists of a tube at¬ 
tached to the mixture outlet, within it sliding 
another tube moved by the governor as that 
expands or contracts with the speed of the 
engine. There are openings in the sides of 
both tubes, but when the sliding tube is at 
its inmost position these are not in line, and 
consequently are closed. When the governor 
acts with increased engine speed, the sliding 
tube is drawn out, and one or more openings 
come into line, air entering through them to 
the mixing chamber. The faster the engine 
runs, the larger become the openings, and in 
consequence the greater is the amount of air 
that they admit. The illustration shows the 



74 


Fig. 26.—Mechanically Controlled Carburetor. 



































































































































































































































CABBURETION 


75 


ball type of gasoline valve, the ball on the 
end of the valve stem being drawn against 
its seat as the float rises. 

While these types are in practically uni¬ 
versal use for automobile engines, there are 
other methods by which the proportions of 
the mixture may be maintained. In one form 
the gasoline drops on a funnel made of fine 
wire gauze, which is placed in the mixing 

9 

chamber in such a manner that the air in en¬ 
tering passes through it. The liquid forms a 
film over the gauze, and is picked up by the 
air, as it is in a condition that permits it to 
evaporate rapidly. In surface carburetors 
air is forced through the gasoline tank, or 
through an absorbent material soaked with 
gasoline, and becomes thoroughly saturated. 
This mixture is then thinned with pure air 
until the desired proportion is obtained, 
when it passes to the combustion space. The 
objections to these forms arise from the clog¬ 
ging of the parts with the impurities present 
in gasoline, and while they give excellent re- 


76 


MOTOR CAR PRINCIPLES 


suits when new, they deteriorate rapidly and 
present such resistance to the flow of the air 
current that they become useless. 

Practically all the carburetors on the mar¬ 
ket are combinations of a few forms of float 
valves, auxiliary air inlets, and spray noz¬ 
zles. In addition to the forms shown in Fig¬ 
ures 24 and 25, the most usual float valves 
may be seen in Figure 27. In the first two 
types shown in this diagram, the float valve 
stems are separate from the floats, and are 
sufficiently heavy to shut off the flow of gaso¬ 
line by their weight. In the third type, the 
gasoline enters the float chamber from the 
top, and as the valve stem is attached to the 
float, the rising of the float results in the 
shutting off of the gasoline. The fourth type 
is in use on carburetors with central mixing 
chambers, the float being hinged to one wall 
of the float chamber. The loose valve stem 
is supported by the hinge, and rises to a seat 
in the valve when the gasoline is at the 
proper depth on the float chamber. 



77 


Fig. 27.—Types of Float Valves. 




































































































































78 MOTOR CAR PRINCIPLES 


Figure 28 illustrates the most usual forms 
of auxiliary air inlets. In the first type, the 
valve disk slides on the valve stem, and en¬ 
larges the size of the main air inlet. All of 
the air thus passes the spray nozzle. In the 
second type, the inlet for the auxiliary air is 
separate from the main air inlet, the two cur¬ 
rents meeting in the mixing chamber, and 
the extra air diluting the rich mixture that is 
formed at the spray nozzle. This action is 
more correct in theory than that of the pre¬ 
ceding type, and better practical results are 
obtained from it. These air valves are de¬ 
fective in opening and closing too abruptly, 
and in tending to vibrate rather than to re¬ 
main open a fixed distance. The air inlet 
illustrated in the fourth diagram was de¬ 
signed to overcome these faults. When the 
engine is not operating, the air inlets are 
closed by a hollow piston that is held up by 
a spring. The upper part of the piston rod 
carries a metal disk that is attached by a 
flexible leather washer to the walls of an up- 



79 


Fig. 28 . Types of Auxiliary Air Inlets. 












































































80 


MOTOR CAR PRINCIPLES 


per chamber. The portion of the chamber 
above the disk is tightly closed, except for a 
small hole in the cover that provides the only 
communication between the atmosphere and 
the air confined in the chamber. When the 
engine runs at speed, the atmospheric pres¬ 
sure against the upper side of the disk is 
greater than the pressure against the lower 
side, and the disk is therefore forced down¬ 
ward against the action of the spring. The 
movement of the disk moves the piston, and 
as this latter slides downward it uncovers 
the openings and admits air. The small size 
of the opening in the cover prevents air from 
entering or leaving the chamber above the 
disk rapidly, and the movement of the piston 
is therefore steady and free from jerks. The 
third diagram illustrates two positions of a 
mechanically operated auxiliary air inlet, 
controlled by a governor. 

There are two methods of supplying the 
carburetor with gasoline. Of these the most 
usual is the gravity feed, in which the tank 


CARBURETION 


81 


is placed at a higher level than the car¬ 
buretor, so that the gasoline flows down to it. 
The tank is usually placed under the seat, 
and the piping so arranged that the car¬ 
buretor is the lowest point of the system. 
This method of feeding is satisfactory if the 
tank can be placed sufficiently above the car¬ 
buretor to have the flow unaffected by an or¬ 
dinary hill, but if it is not so placed, a steep 
ascent may tilt the car to such an extent that 
the carburetor is above the level of the gaso¬ 
line in the tank, in which case the flow of 
course ceases. 

The pressure feed, which is in general use 
on high-grade cars, operates through the 
maintenance of pressure in the supply tank, 
the gasoline being forced out without regard 
to gravity. The tank is tight, so that the 
pressure cannot escape, and is connected by 
a long pipe of small diameter either with the 
combustion space of one of the cylinders or 
with the exhaust pipe, so that the pressure 
of the burned gases is maintained in it. As 


HAND CONTROL 



82 


Fig. 30. Pressure Gasoline Feed. 




























































































CARBURETION 


83 


tlie pressure cannot exist until the engine is 
running, a hand air pump is usually pro¬ 
vided, by which a sufficient pressure may be 
produced in the tank to force out enough 
gasoline for starting. It is necessary to use 
as long a pressure pipe as possible, in order 
to prevent the possibility of flame passing 
through it to the supply of fuel, a long pipe, 
exposed to the air, cooling the gases to such 
an extent that they cannot ignite the gaso¬ 
line. 

The pressure pipe is always fitted with a 
check and relief valve, which acts as a safety 
valve in preventing the pressure in the tank 
from reaching a point at which the joints 
might be strained, and also retains the pres¬ 
sure which would otherwise escape when the 
engine stops. A check and relief valve is 
shown in Figure 31. It is placed in the pres¬ 
sure pipe, the gas or air that supplies the 
pressure acting in the direction of the ar¬ 
rows. The gas can lift the check valve and 
flow past it, but cannot return because the 


84 


MOTOR CAR PRINCIPLES 


valve will come to a seat and close the pas¬ 
sage. The relief valve is held on its seat by 
an adjustable spring, and controls an open¬ 
ing to the outer air. When the pressure 



against the under side of the relief valve be j 
comes greater than the pressure of the 
spring, the valve will be forced open. It may 
be adjusted to retain any desired pressure, 
and will ‘ 1 blow off ’ ’ when the pressure rises 
above this point. 

In some cars an auxiliary gasoline tank is 













































































CARBURETION 


85 


provided on the dash, being fed by pressure 
from the main tank, and from which gasoline 
flows to the carburetor by gravity. The short 
distance of this tank from the carburetor and 
its elevation prevent the possibility of the 
flow being stopped by any tilting of the car 
short of an upset. 

Because of the liability of the presence of 
water in the gasoline, as well as dirt and 
grit, the gasoline line should be fitted with 
a strainer, or trap. This may be in any posi¬ 
tion, but it is usual to have it close to the 
carburetor, if not built into it. The simplest 
strainer consists of a number of thicknesses 
of fine wire gauze, so arranged that it may 
be easily taken out for cleaning. This will 
separate the dirt from the gasoline, and wa¬ 
ter may be caught in a trap, which is a 
pocket where the water, being heavier than 
the gasoline, may settle and be drawn off. 


CHAPTER VI 


IGNITION PRINCIPLES 


A GASOLINE engine derives its power 
from the heat that is produced by 
the burning of the charge of mix¬ 
ture. Each charge that is taken into the 
cylinder is capable of producing a certain 
quantity of heat, but the power that the en¬ 
gine will develop from the charge will de¬ 
pend upon how much of the heat is employed 
in the driving outward of the piston. Some 
of the heat must inevitably be lost. The ex¬ 
haust gases are hot, and the water in the 
cooling system becomes heated; the heat that 
thus passes away is not available for the 
production of power. All that the engine 
designer, builder and user can do is to keep 
these losses as low as possible. 

In order to make the engine run under the 
best possible conditions, the mixture should 

86 


IGNITION PRINCIPLES 


87 


be set on fire and made to give up all of its 
beat when the piston is at the top of the com¬ 
pression stroke and ready to move down on 
the power stroke. The charge would then 
be most highly compressed, and the heated 
gases would exert the greatest possible pres¬ 
sure in striving to expand. This cannot be 
done, however, for there is no method by 
which the entire charge can be ignited and 
made to burn as instantaneously as would be 
necessary. 

The setting on fire, or ignition, of the mix¬ 
ture is done by passing an electric spark 
through it. This spark ignites the particles 
of mixture with which it comes into contact, 
and the flame thus started spreads through 
the entire charge. The flame spreads very 
rapidly, but the high speed at which the pis¬ 
ton moves requires the allowance of a certain 
time between the instant when the spark 
passes and the instant when the entire 
charge is on fire. 

The condition to be sought is to have the 


88 


MOTOR CAR PRINCIPLES 


piston at top center of the compression 
stroke at the instant when the entire charge 
is in flame, for the greatest quantity of heat 
is then produced, and the piston is conse¬ 
quently under the greatest possible pressure. 
If there were some way to set fire to all of 
the particles of mixture at the same time, so 
that the entire charge would burst into 
flame, ignition should be made to occur when 
the piston is at top center. As there is no 
way of doing this, and as it is necessary to 
allow time for the flame to spread through 
the mixture, ignition is made to occur while 
the piston is on the compression stroke; the 
piston will thus be moving upward while the 
flame is spreading, and will reach top center 
at the instant when all of the mixture is in 
flame. 

In consequence of this, some of the heat 
will be wasted, for it will be produced while 
the piston is moving upward on the compres¬ 
sion stroke. The result of producing heat at 
this time will be, in the first place, to check 


IGNITION PRINCIPLES 


89 


tlie movement of the piston, and, in the sec¬ 
ond place, to leave less heat to act against 
the piston during the power stroke. 

If ignition is caused to occur when the pis¬ 
ton is at top center, the piston will have 
moved part way down on the power stroke 
before the whole charge is on fire. As the 
space above the piston in which the heat is 
acting is then large, the pressure on the pis¬ 
ton will be small, and, as a result, the engine 
will deliver very little power. By causing 
ignition to occur while the piston is still on 
the compression stroke, so that the whole 
charge becomes ignited as the piston reaches 
top center, the space above the piston will be 
small; the pressure on the piston will conse¬ 
quently be great, and the engine will deliver 
full power. If ignition occurs too early in 
the power stroke, full pressure will be pro¬ 
duced before the piston reaches top center, 
and will be great enough to check the piston 
or even to stop it. 

The point in the stroke at which ignition 



90 MOTOR CAR PRINCIPLES 


should occur depends principally on the 
speed at which the engine runs, but is also 
N affected by the quality of the mixture. The 
time that must elapse between the passing 
of the spark and the instant when all of the 
mixture is on fire does not change with 
the speed of the engine. In consequence the 
point in the compression stroke at which the 
spark passes must change in accordance with 
changes in engine speed, in order that com¬ 
bustion may be complete when the piston 
reaches the end of the stroke. As an illus¬ 
tration, the spark must occur later in the 
stroke when the piston is moving slowly 
than when it is moving fast. Thus, when an 
engine is being started, the spark should not 
occur until the piston is practically at top 
center, for the piston will then be moving so 
slowly that there is ample time for the flame 
to spread throughout the mixture before the 
power stroke is started. When the engine 
speed increases, the spark must be made to 
occur earlier in the stroke. 


IGNITION PRINCIPLES 


91 


When the spark is produced late in the 
stroke, it is said to he retarded; and it is 
advanced by being made to occur earlier in 
the stroke. 

A mixture that is correct in its proportions 
burns more rapidly than one that is too rich 
or too poor. An improperly adjusted car¬ 
buretor requires the spark to be advanced 
more than would be necessary with a proper 
mixture, and thus makes the engine lose 
power. The proper advance to give the 
spark can only be determined by experience, 
and it is not unusual to have an engine in¬ 
jured by being run for long periods with the 
spark advanced too much or too little. In 
the first case, combustion will be complete 
before the piston reaches top center, and the 
crank shaft and connecting rod bearings will 
be unduly worn by the excessive strain; in 
the second case, the piston will have moved 
downward on the power stroke for a consid¬ 
erable distance before combustion is com¬ 
plete, and the engine will become overheated. 



92 


MOTOR CAR PRINCIPLES 


Small engines may frequently be operated 
with fixed ignition; that is, the point in the 
stroke at which ignition occurs cannot he 
varied. This point will be sufficiently close 
to top center to prevent the danger of a 
“ kick-back ” on starting, but at the same 
time will be far enough advanced for gen¬ 
eral operation. On engines with small and 
compact combustion spaces this system is en¬ 
tirely practical (provided a proper ignition 
system is used) for the time required for the 
spread of the flame is of little moment. 

In some cases, the use of fixed ignition may 
not permit the engine to produce its greatest 
output, but the system is none the less ad¬ 
vantageous in simplifying the engine control. 
It is the tendency of inexpert drivers to ad¬ 
vance the spark too greatly, which results in 
the rapid wear of the engine parts; for this 
reason, fixed ignition is of particular advan¬ 
tage for commercial cars. 

A great number of methods of igniting the 
mixture have been tried, but the system that 


IGNITION PRINCIPLES 


93 


has come into universal use on automobile 
engines is known as the jump spark, or high 
tension, system. In this, an electric current 
is caused to jump between two pieces of 
metal located in the cylinder, and the spark 
that is formed is sufficiently hot to set on fire 
the particles of mixture with which it comes 
into contact. 

The jump spark ignition system is made in 
many forms, but all have certain features in 
common. These are the generator that pro¬ 
duces the electric current that forms the 
spark, the timer or circuit-breaker that con¬ 
trols the instant at which the spark occurs, 
and the spark plug at which the spark is 
formed. 

In order to understand the action and re¬ 
lation of these parts, and to keep the system 
in proper order, it is necessary to know 
something of the principles of electricity and 
of electric currents; a brief explanation is 
thus given. 

Electricity is understood to be a natural 


94 MOTOR CAR PRINCIPLES 


force that exists in everything, but in its 
normal condition it is at rest, and is not no¬ 
ticeable. To make use of electricity it must 
be set in motion, and it is moving electricity, 
or, in other words, an electric current, that 
operates an electric light or an electric mo¬ 
tor, or that produces an ignition spark. 

An electric generator is nothing more nor 
less than a device to make electricity move, 
and thus to produce an electric current. A 
generator sets the electricity in motion by 
raising its pressure. Similarly, steam is 
caused to flow by raising its pressure, and it 
flows from the boiler, where the pressure ex¬ 
ists, to the outer air, where the pressure is 
low. A steam engine is made to run by plac¬ 
ing it in the path of the current of steam, 
and requiring the steam to flow through it 
in order to get to the open air. 

An electric generator has two connections, 
or terminals, at one of which the pressure is 
high, while at the other the pressure is low. 
If there is a path between the two, an electric 


IGNITION PRINCIPLES 


95 


current will flow from the high pressure ter¬ 
minal to the low pressure terminal as long as 
the generator is operating. These terminals 
are given names by which they may be dis¬ 
tinguished, the high pressure terminal being 
called the positive or plus ( + ) terminal, 
while the low pressure is called the negative 
or minus (—) terminal; the current always 
flows from positive, or plus, to negative, or 
minus. 

All electrical apparatus: motors, lamps, 
measuring instruments, bells, and so on, are 
so constructed that they operate when an 
electric current flows through them. To 
make them work, they are placed in the path 
of an electric current, which must flow 
through them in order to get from the posi¬ 
tive terminal of its generator to the negative 
terminal. 

The path provided for the current is made 
of metal or of carbon, for electricity will flow 
over these materials without difficulty; cop¬ 
per wire is generally used for the path, be¬ 
cause electricity will flow over copper more 


96 


MOTOR CAR PRINCIPLES 


easily than over any other common material. 
The path cannot be made of rubber, mica, 
wood, china, cloth or string, for these ma¬ 
terials will not permit the current to flow 
over them; they are known as insulators, or 



non-conductors, and are used to keep the cur¬ 
rent on its proper path. 

Figure 32 is a diagram showing a water 
pump driven by an engine; the pump 
raises water from a tank and forces it 
through a pipe. In flowing out of the end of 
the pipe the water strikes a water-wheel, and 
makes it revolve; after passing the wheel the 
water returns to the tank, from which it will 




































































IGNITION PRINCIPLES 


97 


again be pumped through the pipe. By ex¬ 
erting pressure, the pump sets the water in 
motion, and the moving water does work in 
making the wheel revolve. 

Electricity acts in a similar manner; the 



Fig. 33.—Electric Circuit. 

generator starts it in motion, and the mov¬ 
ing electricity, or electric current, operates 
the bell, or lamp, or whatever apparatus may 
be in its path, finally returning to the gen¬ 
erator (Fig. 33). If the current is prevented 
from returning to the generator by the break¬ 
ing of a wire, or for any other reason, the 
flow of current stops. 

The path provided for the current is called 
the circuit; if the current can leak from the 
















98 


MOTOR CAR PRINCIPLES 


circuit and return to the generator without 
doing the work that it is expected to do, the 
leak is called a short-circuit. It is apparent 
that short-circuits are wasteful, and that 
they should he prevented. The circuit is there¬ 
fore insulated, or, in other words, the path is 
supported and surrounded by insulating ma¬ 
terial that will make leakage impossible. 

Electric currents are measured very much 
as streams of water are measured; that is, a 
measurement is made of the pressure that 
forces the current to flow, and another meas¬ 
urement is made of the quantity of electricity 
that flows. It is the quantity of electricity 
that does work; the greater the quantity, the 
more will be the work done. 

In order to make an electric lamp burn, a 
definite quantity of electricity must be forced 
through it, and in order that the required 
quantity may be forced through the lamp, it 
is necessary to have the electricity under 
equally definite pressure. This applies not 
only to lamps, but to all electrical apparatus. 


IGNITION PRINCIPLES 


99 


For example, it will be noticed that a Bosch 
coil bears the mark “ 6 volts this indi¬ 
cates that in order to force through it the 
quantity of electricity necessary to make it 
work properly, the current must be under a 
pressure of six volts. 

Electrical pressure is measured in volts, 
and the higher the pressure, or voltage, the 
greater will be the quantity of electricity 
that is forced over the circuit. A very low 
pressure will be sufficient to force a current 
over a circuit that is made of metal, but if 
the circuit has in it even a very small air 
space, as, for instance, the ends of two wires 
held close together, the pressure necessary 
to force the electricity over it will be many 
thousands of volts. Air is one of the best of 
insulators; that is, it presents very great re¬ 
sistance to the flow of current, and special 
apparatus is necessary to produce enough 
pressure to force the current through it. 

The quantity of electricity that flows in a 
circuit is measured in amperes. The higher 


> * i 

> ) > 



100 MOTOR CAR PRINCIPLES 


the voltage, the greater will be the amperage 
of the current that is forced over the circuit. 

If hot water is used in the pump shown in 
Figure 32, the pipe will become heated, and 
so will the air surrounding the pipe. When 
an electric current flows over a wire, it af¬ 
fects the air that surrounds the wire, for the 
air becomes charged with magnetism. 

Everyone has played with a magnet, and 
knows that, while it has the ability to attract 
to it pieces of iron and steel, it has no effect 



Fig, 34.—Magnetism from Electricity. 




i 


i 


< 


c 

t 

( t 

c i 
.1 < < 

























IGNITION PRINCIPLES 


101 


on copper, wood, rubber or any other ma¬ 
terial. A pile of iron filings may be stirred 
with a copper wire without being affected in 
the slightest degree, but if an electric cur¬ 
rent is passing through the wire, the filings 
will cling to the wire as if it were a true steel 


magnet. (Fig. 34.) 

A piece of iron that 
is near a magnet will 
become magnetized 
itself, and will be 
able to attract other 
pieces of iron and 
steel, but it loses this 
ability when the mag¬ 
net is removed. (Fig. 
35.) This is one of 
the points of differ- 
e n c e between iron 
and steel, for iron 
gains magnetism 
very easily, but can¬ 
not retain it, while 



Fig. 35. —Magnetizing a 
Piece of Iron. 








102 MOTOR CAR PRINCIPLES 


steel gains magnetism with difficulty, but re¬ 
tains it indefinitely. 

If a wire through which an electric current 
is flowing is wound around an iron bar, the 



Fig. 36.—Magnetizing Iron by Electricity. 


iron will become a magnet and will remain 
a magnet for just as long as the current 
flows. (Fig. 36.) The bar will lose its mag¬ 
netism the instant that the current stops 
flowing. 

Magnetism can thus be produced from 
electricity, and, conversely, electricity can be 































































































IGNITION PRINCIPLES 


103 


produced from magnetism. Figure 37 shows 
an iron bar with a wire wound around one 
end, this wire being connected with a gen¬ 
erator so that an electric current can be 
passed through it; around the other end of 



the bar is wound a second wire in no way 
connected with the first. When the current 
is not flowing, there will be no magnetism in 
the bar, but when the circuit is closed, the 
bar will become magnetized by the magnet¬ 
ism produced by the flow of current in the 
wire. The bar will begin to become mag¬ 
netized the instant that the current starts 


























104 MOTOR CAR PRINCIPLES 


flowing, and its magnetism will get stronger 
and stronger until it reaches the greatest 
strength that can be produced by the quan¬ 
tity of current. The bar will remain mag¬ 
netized as long as the current continues to 
flow, but the magnetism will die away very 
abruptly the instant that the flow of current 
stops. 

If the current weakens, the strength of the 
magnetism will weaken also; any change in 
the strength of the current will be accom¬ 
panied by a corresponding change in the 
strength of the magnetism of the bar. 

Whenever the magnetism of the bar 
changes strength, an electric current will ap¬ 
pear in the second wire, and the strength of 
this new current will be in accordance with 
the extent to which the strength of the mag¬ 
netism changes. Every slightest change in 
the strength of the magnetism produces a 
current, and the current will be strongest 
when the change from weak to strong or 
from strong to weak is most abrupt. 


IGNITION PRINCIPLES 105 

When the circuit of the first wire is closed 
and the generator current starts flowing, the 
bar rapidly becomes magnetized to full 
strength, and remains at full strength while 
the current continues to flow; the new cur¬ 
rent will flow in the second wire while the 
change is going on, but the flow will stop 
the instant that the strength of the magnet¬ 
ism stops changing. 

On the breaking of the generator circuit, 
the magnetism will die away very abruptly, 
and while it is dying the new current will 
again flow in the second wire. 

It is thus seen that the new current is pro¬ 
duced, or induced, only while the magnetism 
is changing strength. It makes no difference 
how the bar is magnetized; it may be mag¬ 
netized by an electric current, as described, 
or by a steel magnet, or by any other method 
that will permit the strength of the magnet¬ 
ism to be changed. 

The necessity for this explanation of mag¬ 
netic principles becomes clear when it is un- 


106 MOTOR CAR PRINCIPLES 


derstood that the ignition spark is always 
produced by magnetism, and that when a 
battery is used its current is required to pro¬ 
duce magnetism, which in turn induces the 
current that forms the ignition spark. 


CHAPTER VII 


MAGNETO PRINCIPLES 


I T is almost invariably the case that on 
automobile engines the ignition spark 
is produced by a generator called a 
magneto. This is a machine containing pow¬ 
erful steel magnets, with an iron bar that is 
arranged to revolve between the ends of the 
magnets in such a manner that it is contin¬ 
ually being magnetized and demagnetized. 
The changes in the strength of the magnet¬ 
ism of the bar induce electric currents in a 
wire wound around it, and it is these cur¬ 
rents that produce the ignition spark. 

The revolving bar is called the armature, 
and its shape is shown in Figure 38. The 
only part to which attention need be paid is 
the core; the heads act to direct the magnet¬ 
ism to the core, and it makes no difference in 
the action of the magneto whether or not 

107 


108 MOTOR CAR PRINCIPLES 


they are magnetized. The heavy line in the 
diagram indicates the position of the wire; 
in an actual armature the amount of wire 



Fig. 38.—Armature. 


used will fill the entire space between the 
heads. 

The flow of magnetism is indicated by the 
arrows in Figure 39, which is a diagram of 
the end of a magneto and of the armature; 
the armature is shown in four positions while 
making a half-revolution. In positions A, B 
and D, the magnetism, in flowing from one 
end or pole of the magnet to the other, finds 
its easiest path through the armature core, 
while in position C the easiest path is 
through the armature heads. It is in passing 
from one of these positions to another that 














MAGNETO PRINCIPLES 


109 


the magnetism of the armature changes 
strength, with the result that electric cur¬ 
rents are produced in the armature winding. 

In the following explanation, it must be 
borne in mind that magnetism alone will not 



Fig. 39.—Flow of Magnetism in Armature. 

produce an electric current; it is necessary 
for the magnetism to be changing in 
strength. In order to produce a current that 
is sufficient to form an ignition spark, there 
must be a very considerable change in 
strength, and the change must occur 
abruptly. 

When the armature is not revolving, no 
current is produced, for, while the core may 




























110 MOTOR CAR PRINCIPLES 


be magnetized, the magnetism is not chang¬ 
ing its strength. When the armature is re¬ 
volved, the magnetism of the core continu¬ 
ally changes its strength, and twice during 
each revolution the strength changes com¬ 
pletely, going from full strength to no 
strength and back again. The faster the 
armature is driven, the more abrupt these 
changes will be, and the currents produced 
at high speed will consequently be more in¬ 
tense than those produced at low speed. 

Referring to Figure 40, which shows the 
positions of the armature during a complete 
revolution, the armature in position A is in¬ 
tensely magnetized, for practically all of the 
magnetism of the magnets then flows 
through the core. In position B, most of it 
continues to flow through the core, but it is 
beginning to find it easier to flow through 
the heads and across the air space. In posi¬ 
tion C the easiest path is through the heads, 
and the magnetism entirely abandons the 
core, which now has no strength. When the 


MAGNETO PRINCIPLES 


111 


armature moves from position A to position 
C, the magnetism of the core completely dies 
away, but it returns as completely when the 




E. Mo. Current. F. Weak Current. G. Intense Current. H. Weak Current. 
Fig. 40.—Production of Current in Magnets. 


armature moves from position C toward po¬ 
sition E. During the second half of the revo¬ 
lution there will be another complete change 
in strength. 

When the armature passes from position H 
to position B, or from position D to position 












































112 MOTOR CAR PRINCIPLES 


F, there is only a slight change in the 
strength of the magnetism, and the current 
then produced will be too weak to form an 
ignition spark. When the armature passes 
from position B toward position D, or from 
position F toward position H, the change in 
the strength of the magnetism is very great; 
it is greatest as the armature passes over 
positions C and G, and it is then that the cur¬ 
rent is sufficiently intense to form an ignition 
spark. 

In former types of magnetos the most in¬ 
tense spark was produced just as the arma¬ 
ture left position C or position G. A spark 
could be produced at any point between posi¬ 
tions C and D, and between positions G and 
H, but the closer the armature approached 
D and H, the faster it was necessary to drive 
it in order to obtain a sufficiently intense 
spark. The magneto was set in such relation 
to the engine crank shaft that the most in¬ 
tense spark occurred when the piston was on 
the compression stroke and approaching top 


MAGNETO PRINCIPLES 


113 


center; the spark was then fully advanced. 
When cranking the engine, or running it 
slowly, it would be necessary to produce the 
spark later in the stroke, or even at top cen¬ 
ter, to prevent back firing; by the time the 
piston reached top center, however, the 
armature would have moved from position 
C to position D, and would have to be turn¬ 
ing at high speed in order to give a spark. 

To make it easier to crank an engine, or to 
run it slowly, it is advantageous to have a 
magneto so constructed that it gives a spark 
at as low a speed in the fully retarded posi¬ 
tion as when fully advanced. In Bosch mag¬ 
netos this is accomplished by means of ex¬ 
tensions on the pole shoes, somewhat like 
broad teeth. This is shown in Figure 41. 

In applying a magneto to an engine, it 
must be remembered that the engine requires 
a spark to be produced at a certain point in 
the stroke, and also that the magneto will 
give a spark at definite points in the rota¬ 
tion of the armature; clearly, then, the crank 


114 MOTOR CAR PRINCIPLES 


shaft and the armature must run in such re¬ 
lation that the armature is giving a spark at 
the instant when the engine requires one. 




















MAGNETO PRINCIPLES 


115 


A four-cylinder, four-cycle engine will re¬ 
quire two sparks during each revolution of 
the crank shaft, and as a magneto will deliver 
two sparks during each revolution of the 
armature, it will be seen that for such an en¬ 
gine the armature must be driven at the same 
speed as the crank shaft. A 6-cylinder, 
4-cycle engine requires three sparks during 
each revolution of the crank shaft; in pro¬ 
ducing three sparks the armature must make 
iy 2 revolutions, and it is thus apparent that 
for such an engine the armature must be 
geared to run at 1 y 2 times the crank shaft 
speed, or, in other words, it must make three 
revolutions while the crank shaft makes two. 

A single cylinder 4-cycle engine requires 
but one spark during every two revolutions 
of the crank shaft. Theoretically, its mag¬ 
neto should be driven at one-quarter the 
speed of the crank shaft, so that it makes 
one-half of a revolution while the crank shaft 
makes two. Practically, this speed would be 
so slow that the magneto might not produce 


116 MOTOR CAR PRINCIPLES 


a spark at the speed at which the engine is 
cranked, and the armature is therefore 
driven at one-half the crank shaft speed. The 
magneto is so arranged that it gives only one 
spark during each revolution, instead of two. 

When a magneto is used on an engine 
with a number of cylinders it must be so 
arranged that it distributes its sparks among 
the various cylinders as required by the 
firing order, and this is done by a device 
known as a distributor. A distributor con¬ 
sists of a brush, usually in the form of a 
piece of carbon, that is attached to a re¬ 
volving part of the magneto. As this brush 
revolves it comes into contact with one after 
the other of a series of metal blocks, there 
being one block for each cylinder. At the 
instant when the magneto is giving a spark, 
the brush will be in contact with one of the 
blocks, and the sparking current will pass 
from the armature to the brush, to the block, 
and to the cylinder where the spark is to 
be formed. By the time that the next cylin- 


MAGNETO PRINCIPLES 


117 


der requires a spark, the armature will have 
made one-half of a revolution, and the dis¬ 
tributor brush will have moved to the next 
block. 

In 4-cycle engines, the distributor makes 
one revolution to two of the crank shaft, 
no matter how many cylinders the engine 
may have; in other words, the distributor 
runs at cam shaft speed. In 2-cycle en¬ 
gines the distributor runs at crank shaft 
speed. The distributor is built into the mag¬ 
neto, and is geared to the armature shaft and 
driven by it. Diagrams of distributors for 
different numbers of cylinders are shown in 
Figure 42. 

Ignition magnetos are further fitted with 
a device known as the circuit breaker, or in¬ 
terrupter, which is connected to the arma¬ 
ture winding, and controls the instant at 
which the spark occurs. A circuit breaker 
consists of a block of metal carefully in¬ 
sulated from the metal of the magneto, com¬ 
bined with a lever that is so pivoted that it 



DISTRIBUTOR RING 


LEVER 


BRUSH 


DISTRIBU¬ 

TOR 

PLATE 



118 


























































MAGNETO PRINCIPLES 


119 


may touch the insulated block or move away 
from it. The lever is pivoted to the metal of 
the magneto, so that a current that flows to 
the lever may pass to the metal of the mag¬ 
neto; or, in other words, to ground. The in¬ 
side end of the armature winding is 
grounded by being screwed to the armature 
core, so that a current may pass from the 
core to the winding; the outer end of the 
winding is attached to the insulated block 
of the circuit breaker. 

When the lever touches the insulated 
block, a current produced in the armature 
winding lias a complete circuit in which to 
flow, for it may pass to the insulated block, 
to the lever, to ground; or, in other words, 
to the metal of the magneto, and thence to 
the armature core and back to the winding. 
When the lever moves away from the block, 
this circuit is broken, and the current is 
forced to seek another path by which to re¬ 
turn to the armature winding. 

In ignition magnetos, the circuit breaker 


120 MOTOR CAR PRINCIPLES 


holds the circuit closed during all of the time 
when the current is weak. When the arma¬ 
ture reaches positions C or G, or some point 
just beyond them, the lever is separated from 
the insulated block, and the intense current 
that is then flowing is diverted in such a 
manner that it forms an ignition spark. 

The principle of a circuit breaker is shown 
in Figure 43. The lever is shown as a 
straight bar, pivoted at one end, and with a 
platinum point at the other end that may 
touch a corresponding platinum point on the 
insulated block. These parts are supported 
on the end of the magneto in such a manner 
that when the armature revolves, a cam on 
its shaft touches the lever and makes it 
move away from the insulated block. The 
cam has two projections, so that it will cause 
the lever to move twice during each revolu¬ 
tion of the armature. 

It has been explained that a magneto can 
give a spark at any point from position C 
to position D, and from position G to posi- 


CONTACT plate: 




121 


Fig. 43.—Principle of Spark Advance. 








































122 MOTOR CAR PRINCIPLES 


tion H. In order to produce a spark, the 
circuit breaker must break the circuit at 
some point in this range, and this is under 
the control of the driver. As indicated in 
Figure 43, the circuit breaker is so mounted 
that it may be turned on the end of the mag¬ 
neto, just as the cover of a pill box may be 
turned, but it may be turned only through a 
short distance; this permits the advance and 
retard of the spark. When the circuit 
breaker is turned as far as it will go in the 
opposite direction to the way that the arma¬ 
ture is turning, as indicated in the first 
sketch (Fig. 43), the lever will be moved 
when the armature is passing position C or 
C, and the spark will be advanced. When 
the circuit breaker is moved as far as it will 
go in the same direction as the armature is 
turning, the lever will not be moved until 
the armature has reached position D or H, 
as indicated in the second sketch, and the 
spark will be retarded. 

Figure 43 also shows a distributor, and it 


MAGNETO PRINCIPLES 123 

will be seen that the advance and retard of 
the spark will not move the distributor brush 
out of contact with the proper block. 

A magneto is set on the engine so that the 
circuit breaker lever is beginning to move 
in the fully retarded position when the pis¬ 
ton is at top dead center. Peculiarities of 
engine construction may make a difference 
in the setting of the magneto, however, and 
the setting that will give the greatest power 
can usually be determined only by experi¬ 
ment. 

A magneto is so arranged that the produc¬ 
tion of sparks may be stopped, and this is 
usually done by giving the armature current 
a path by which it may flow, regardless of 
whether the circuit breaker is open or closed. 
Having such a path, the movement of the cir¬ 
cuit breaker does not affect the flow of cur¬ 
rent, and the production of sparks ceases. 

The insulated block is connected to one 
side of a switch, the other side of which is 
grounded by being connected to the metal 


124 MOTOR CAR PRINCIPLES 


of the engine. To produce ignition this 
switch must be open; to cut out ignition the 
switch is closed. 

Ignition magnetos may be divided into two 
classes; those that produce their own spark¬ 
ing currents directly in the armature, and 
those whose currents have not sufficient pres¬ 
sure to form a spark, and that require to be 
intensified by means of a device called a 
transformer coil. The first is called the true 
high tension type, and the second is the 
transformer or step-up type; of the two, the 
true high tension magneto is in more general 


use. 


CHAPTER VIII 


TRUE HIGH TENSION MAGNETOS 

HE distinguishing feature of the 



true high tension magneto is the 




armature winding, which is made 


up of a few layers of coarse wire, and on top 
of these a very great number of layers of tine 
wire. The circuit breaker is connected only 
to the coarse wire, which forms the primary 
winding; the tine wire forms the secondary 
winding, and it is in this that the sparking 
current is generated. 

The relation of these parts is shown in 
Figure 44. One end of the primary winding 
is shown attached to the insulated block of 
the circuit breaker, while the other leads to 
the circuit breaker lever; when the circuit 
breaker makes contact, a current may flow in 
the primary winding. One end of the sec¬ 
ondary is connected to one end of the pri- 


125 



CIRCUIT BREAKER 

Fig. 44.—Principle of True High Tension Magneto. 


126 










































HIGH TENSION MAGNETOS 127 


mary, so that the secondary is in effect a 
continuation of the primary; the other end of 
the secondary is shown as brought close to a 
wire attached to the remaining end of the 
primary. In order that current may flow in 
the secondary circuit it must thus jump 
across the gap between the ends of the wires, 
and pass through the primary to the point 
where the primary and the secondary are 
connected. 

During those parts of the rotation of the 
armature when the circuit breaker is closed, 
a current will flow in the primary winding. 
The same changes in magnetism that pro¬ 
duce this current will also tend to produce 
a current in the secondary winding. The sec¬ 
ondary circuit is not complete, however, for 
it is broken by the gap between the ends of 
the wires, and without a complete circuit the 
current cannot flow. Thus there exists in 
the secondary winding a pressure that would 
make a current flow if it was great enough 
to force the electricity across the gap. 


128 MOTOR CAR PRINCIPLES 


As the armature continues to revolve, and 
as it comes closer to position C or position 
G, the current in the primary becomes more 
intense; when the circuit breaker opens, this 
flow of intense current is diverted, for the 
only path then left for it is through the sec¬ 
ondary winding. The extremely abrupt 
change in the strength of the magnetism of 
the armature core due to this diverting of 
the flow of primary current increases the 
pressure in the secondary winding to such 
an extent that it is easily able to jump across 
the gap. In jumping the gap it forms a 
spark of very great intensity. 

In the construction of actual magnetos, the 
inner end of the primary winding is 
grounded; or, in other words, is secured to 
the metal of the armature core. The circuit 
breaker lever is also grounded, for it is 
mounted in such a way that it is in contact 
with the metal of the magneto. A current 
may thus flow through the metal of the mag¬ 
neto from the circuit breaker lever to the 


HIGH TENSION MAGNETOS 129 


armature winding. The outer end of the sec¬ 
ondary winding is connected through the 
distributor to the spark plug, which is 



PLATINUM 
| POINTS 


ADJUSTMENT; 


INSULATED 
X PARD\ 


CAM — 
LEVER 


CONTACT PLATES 


TERMINALS 


DISTRIBUTOR 
BRUSH' 


FIBRE BLOCK 


Fig. 45.—Bosch Magneto, Type D U, End View. 








































































130 MOTOR CAR PRINCIPLES 


screwed into the cylinder and is thus in con¬ 
tact with the metal of the engine. A current 
that forms a spark at the plug passes to the 
metal of the engine, which provides a path 
by which it may flow to the metal of the mag¬ 
neto, to the grounded end of the primary 
winding, and thus may return to the sec¬ 
ondary winding. 

The principle thus outlined is employed in 
Bosch high tension magnetos, which are pro¬ 
duced in a great variety of types, according 
to the requirements of different engines. 
Type D U is in very general use, and an end 
view of this type for a 4-cylinder engine is 
shown in Figure 45. A side view of this 
magneto, partly in section, is shown in Fig¬ 
ure 46. 

The Bosch circuit breaker is arranged on 
a disk that is attached to the armature shaft 
and revolves with it. The lever is L-shaped, 
with the pivot at the angle, and it is caused 
to move by two steel cam blocks that are 
attached to the inside of the housing that 


D)5TR!3UT0R BRUSH 



131 









































































































































































































































































































132 MOTOR CAR PRINCIPLES 


incloses the circuit breaker. These parts 
may be seen in Figures 45 and 47. By mov¬ 
ing the housing, the lever may be made to 
strike the cam blocks earlier or later in the 



ADJUSTING NUT 
PLATINUM POINTS 


CIRCUIT 

BREAKER 

DISK 


LEVER 
SPRING 


HOUSING 

INSULATED BLOCK 


Fig. 47. —Bosch Circuit Breaker. 


rotation of the armature, which provides for 
the advance and retard of the spark. 

The circuit breaker disk is secured to the 
armature shaft by a long bolt passing 
through its center, and, as may be seen from 
Figure 46, this bolt serves in addition to con- 































HIGH TENSION MAGNETOS 133 


duct the current from the primary winding 
to the insulated block of the circuit breaker. 
In order to remove the circuit breaker the 
bolt is unscrewed; the circuit breaker can¬ 
not be replaced incorrectly, for it is provided 
with a key that fits into a keyway in the 
armature shaft. 

A deeply grooved hard rubber wheel with 
a metal ring in the bottom of the groove is 
attached to the other end of the armature 
shaft. This is the slip ring, by which the 
sparking current flows from the secondary 
winding. The outer end of the secondary 
winding is secured to this ring, and a car¬ 
bon brush is so arranged that the ring passes 
under it in revolving. The sparking current 
passes from the armature to the slip ring 
and the carbon brush, and by a conducting 
bar to the distributor. 

On the dust cover is a device called the 
safety spark gap, which is to the magneto 
what the safety valve is to a steam boiler. 
The safety spark gap consists of a pointed 


134 MOTOR CAR PRINCIPLES 


brass rod set in tlie dust cover and there¬ 
fore grounded, and a second brass rod set in 
the porcelain cover of the gap housing in 
such a manner that the two are separated by 
a fixed distance. The upper rod is connected 
to the brush that presses against the slip 
ring. Any sparking current produced in the 
armature may flow by jumping across the 
spark plug gap, or by jumping across the 
points of the safety spark gap. The distance 
between these points is such that it is easier 
for the current to jump across the spark plug 
gap, and the current therefore takes that 
path whenever it is able to do so. Should 
one of the spark plug cables break or fall off, 
or should the spark plug gap be too wide, the 
magneto current will then pass across the 
safety spark gap. Without the safety gap, 
the current would make a path for itself by 
breaking through the insulation of the arma¬ 
ture winding and jumping to the core, which 
would ruin the armature. 

A spark at the safety gap indicates a fault 



0I5K 

PIVOT- 


PLATINUM 
^ POINTS 


ADJUSTMENT 


CONTACT 

PLATES 


DISTRIBUTOR 

BRUSH- 


TERMINALS' 


ROLLERS 

GROUNDED 

LEVER 


INSULATED 

PART 


Fig. 48. —Bosch Magneto, Types D and D R, End View. 

135 





























































136 MOTOR CAR PRINCIPLES 


in the spark plug circuit, and the fault 

t 

should be located and corrected without loss 
of time. 

The circuit breaker housing or the hous¬ 
ing cover carries a flat spring that presses 
against the head of the long bolt, and is thus 
in connection with the primary circuit. This 
spring is insulated from the magneto, but 
is attached to a binding nut, to which is 
connected a wire that leads to a switch ; an¬ 
other wire leads from the switch to any 
metal part of the engine. By closing the 
switch, a circuit is provided between the in¬ 
sulated block of the circuit breaker and the 
metal of the engine, and as the current will 
then have a path to ground even when the 
circuit breaker is open, the instant result will 
be the stopping of the ignition spark. The 
switch must be open in order that the engine 
may run. 

Bosch magnetos of the D and D R types 
are similar in arrangement, as shown in Fig¬ 
ures 48 and 49. The distributor plate is fixed 



137 


PRIMARY WINDINGS ' 

Fig. 49.—Bosch Magneto, Types D and D B. 













































































































































































































































138 MOTOR CAR PRINCIPLES 


on the magneto instead of being easily de¬ 
tachable, however, and by removing the 
three-armed clamp on its face the distributor 
cover may be removed, and the revolving 
brush and its holder pulled out. The circuit 
breaker lever is operated by two fiber rollers 
instead of by steel cam blocks, as used on the 
D U type. The D U also has two single mag¬ 
nets, while the D has three double magnets 
and the D R two double magnets. 

The Bosch Z R type of magneto is entirely 
different in appearance from those already 
described, although the arrangement and ac¬ 
tion are unchanged. It has the advantage 
of being unaffected by water and dust. To 
provide for this, the magneto is entirely in¬ 
closed, and the terminals are of such a form 
that water cannot cause a short circuit. The 
appearance of the magneto is shown in Fig¬ 
ure 50. 

In some of the forms of the Z R the cables 
are attached as indicated in Figure 51. The 
cable is cut off square, and pushed to the bot- 


OIL 




139 


Fig. 50. —Bosch Magneto, Type Z R. 






























































































































































































140 MOTOR CAR PRINCIPLES 


tom of a hole in the distributor plate or the 
brush holder, in which it fits snugly. A 
pointed screw is then screwed through the 

side wall of the 
hole, piercing the 
cable and connect¬ 
ing the wire with a 
metal block that 
communicates 
with the circuit. 
This also has the 
effect of jamming 
the cable tightly in 

Fig. 51—Cable Connection of the hole. As the 

Bosch Z R Magneto. , , . 

hole does not go 

through, water and dust cannot penetrate to 
the interior of the magneto. 

Figure 52 shows the connections of a 
4-cylinder magneto, and magnetos for any 
number of cylinders are connected in a sim¬ 
ilar manner. Each distributor terminal is 
connected to its proper spark plug, according 
to the firing order of the engine, and the only 








HIGH TENSION MAGNETOS 141 


other wire necessary is the switch connec¬ 
tion. 

A specific rule for the timing, or setting, 
of a magneto cannot be laid down, because 



Fig. 52. —Magneto Connections. 


the variations in engine design and construc¬ 
tion may result in corresponding variations 
in the ignition point. It may be said, how¬ 
ever, that an engine will run if the magneto 
is so set that the fully retarded spark occurs 
when the piston is at top center of its stroke. 
The setting that will give the greatest power 
output can be determined only by inquiry 







































142 MOTOR CAR PRINCIPLES 


of the makers of the engine or by ex¬ 
periment. 

The magneto manufacturers publish com¬ 
plete and detailed instruction books, which 
explain the method of attaching and setting 
of each type of magneto. These books may 
be obtained for the asking. 

Another series of Bosch magnetos is 
known as the 2-spark type, and has for its 
object the production of two sparks each 
time that the circuit breaker opens. As has 
been explained, the time that must elapse be¬ 
tween the passing of the spark and the com¬ 
plete combustion of the mixture causes a 
loss of efficiency, and the engine designer en¬ 
deavors to make the combustion space of 
such a form that the flame will sweep 
through it in the shortest possible time. By 
the use of a 2-spark magneto, ignition may 
be started at two widely separated points in 
the combustion space instead of at but one, 
which greatly reduces the time necessary for 
the complete combustion of the charge. 


HIGH TENSION MAGNETOS 143 


The use of the 2-spark system is especially 
advantageous in engines with wide combus¬ 
tion spaces, such as exist in T-head designs, 
but it may be used with excellent results on 
any form of engine, provided the spark plugs 



Fig. 53.—Effect of Two-spark Ignition. 


are separated by a distance of about half of 
the total width. (Fig. 53.) 

A 2-spark magneto will increase the power 
output by 10 to 15 per cent., and will give 
greater flexibility of operation. 

In single spark magnetos, one end of the 
secondary winding is grounded on the arma¬ 
ture core through the primary winding, but 
on 2-spark magnetos this ground does not 
exist, for the secondary winding is grounded 




























144 MOTOR CAR PRINCIPLES 


through the second spark plug. In order to 
do this, the slip ring is made up of two seg¬ 
ments, each extending about one-quarter the 
way around the slip ring wheel, instead of 
being a continuous band. These segments 


To Sown Plugs 
Nearest To Second Set 

Inlet Yrl ves or Spark Plugs 



Switch Positions /-One Set or Plugs Opera ting 
2-BothSets of Plugs Operating 


high Tension Cable 



ground 

Low Tension Cable 


Fig. 54.—Two-spark Magneto Connections. 


are connected to the ends of the secondary 
winding, and two slip ring brushes are set 
on opposite sides of the end plate. 

The magneto is provided with a distribu¬ 
tor plate of double thickness, which has ter¬ 
minals for the double set of spark plug 
cables leading to the engine. The distribu¬ 
tor brush holder carries two brushes, one for 
each distributor, each brush being connected 

























HIGH TENSION MAGNETOS 145 


to one of the slip ring brush holders. The 
sparking current passes from one of the slip 
ring brushes through its distributor to a 
spark plug, then by the metal of the engine 
to the second spark plug in the same cylin¬ 
der, and returns to the armature by the sec¬ 
ond distributor and slip ring brush. (Fig. 54.) 

The switch used with this magneto has 
three positions, the outside positions being 
marked 2, while the central position is 
marked 1. With the switch in either of the 
outside positions, both sparks will appear, 
while the inside position causes only one 
spark plug to operate. This is done by con¬ 
necting one of the slip ring brushes to the 
switch, and making a further connection be¬ 
tween the switch and one of the distributors. 
With the switch in position 2, the current 
flows from the armature to the distributor 
through the switch; when in position 1 the 
switch passes this current directly to ground, 
and consequently cuts the corresponding 
spark plug out of the circuit. 


146 MOTOR CAR PRINCIPLES 


Position 1 is used in starting the engine 
and for slow running; position 2 is used 
when maximum power is required. 

The arrangement of the circuit breaker is 
not changed, and the sparks are produced 
simultaneously at the instant when the plati¬ 
num points separate. 


CHAPTER IX 


TRANSFORMER MAGNETOS 

HE magneto used on a transformer 



system produces a current so low in 
voltage, or pressure, that it cannot 


break its way through air, no matter how 
small the air space may be. To use such a 
current for a jump spark system, it must be 
transformed to a current of high voltage, and 
this is done by means of an induction coil. 

An induction coil consists of a core of soft 
iron, which is made of a number of pieces of 
iron wire rather than of a solid bar, because 
in that form it will gain and lose magnetism 
more rapidly. Around this core a few layers 
of coarse wire are wound, this forming the 
primary winding; on top of this is the sec¬ 
ondary winding, which is made up of a great 
number of layers of fine wire. An induction 
coil is thus seen to be similar in construction 


147 


148 MOTOR CAR PRINCIPLES 

to the armature of a true high tension mag¬ 
neto. 

When a current flows through the primary 
winding of a coil, the core becomes mag¬ 
netized, and this increase in the strength of 
the magnetism results in the production of a 
high-pressure current in the secondary wind¬ 
ing. When the current stops flowing in the 
primary winding the magnetism of the core 
dies away, and another rush of current is 
produced in the secondary winding. By 
making or breaking the primary circuit very 
abruptly the magnetism is caused to change 
its strength with great suddenness, and the 
currents that are produced in the secondary 
winding will have sufficient pressure to jump 
across the spark plug gap and to form a 
spark. 

In transformer systems, the magneto cur¬ 
rent flows through the primary winding, and 
does not itself form the ignition spark; it 
produces a change of strength in the mag¬ 
netism of the core, and the ignition spark is 


TRANSFORMER MAGNETOS 149 


formed by the current that then appears in 
the secondary winding. 

The best known of the systems that oper¬ 
ate under this principle are the Splitdorf 
and the Remy. 

In the Splitdorf, the magneto current is 
not permitted to flow in the primary winding 
of the coil until it has reached its full in¬ 
tensity; the sudden rush of this intense cur¬ 
rent causes a sufficiently sudden production 
of magnetism around the core of the coil to 
generate a sparking current in the secondary 
winding. 

Figure 55 shows the principle of the Split¬ 
dorf system. The armature core is of the 
usual shape, and is wound with a number of 
layers of coarse wire. One terminal of the 
winding leads to the insulated block of the 
circuit breaker, while the other terminal is 

connected with the circuit breaker lever. 

♦ 

From these two points the connections are 
continued to the two ends of the primary 
winding of the coil, so that the magneto cur- 



150 
































TRANSFORMER MAGNETOS 151 


rent has two paths by which it may flow, one 
being across the platinum points of the cir¬ 
cuit breaker when they are touching, and the 
other being the primary winding of the coil. 

It is much easier for the current to flow 
across the platinum points than through the 
primary winding, and consequently it will 
take that path whenever it can. The plati¬ 
num points will be together while the arma¬ 
ture is moving from position H toward posi¬ 
tion C (Fig. 40), and from position D toward 
position G, and the weak current then being 
produced will take the platinum point path. 
When the armature reaches position C and 
position G, the circuit breaker lever moves 
to separate the platinum points, and the cur¬ 
rent, no longer being able to take that path, 
must flow through the primary winding of 
the coil. The spark is thus produced at the 
instant when the platinum points separate. 

In the actual magneto, the inner end of the 
armature winding is secured to the armature 
core, and is thus grounded; the circuit 


152 MOTOR CAR PRINCIPLES 


breaker lever is pivoted to the metal of the 
magneto, and is also grounded. In addition, 
one end of the primary winding of the coil 
is connected to the metal of the engine, and 
it is thus seen that the metal of the engine 
and of the magneto will serve as a path by 
which the current may return to the arma¬ 
ture winding from the circuit breaker or 
from the coil. 

The outer end of the armature winding is 
attached to a rod that passes lengthwise 
through the armature shaft, but that is in¬ 
sulated from it. The rod projects beyond the 
end of the shaft, and a spring or brush that 
presses against the projecting end conducts 
the armature current to the insulated block 
of the circuit breaker. 

One end of the secondary winding of the 
coil is connected to the primary winding, 
while the other end leads to the distributor. 
The secondary current thus passes to the 
plug, and returns to the secondary winding 
by the metal of the engine and the connection 


TRANSFORMER MAGNETOS 153 


between the engine and the primary winding 
of the coil. 

Figure 56 is an end view of the Splitdorf 
magneto, and it shows the construction of 
the circuit breaker. The circuit breaker 
lever is pivoted at one end to the housing or 

casing, and it is operated by a cam attached 

* 

to the armature shaft. A spring holds the 
lever against the cam, and a roller on the 
lever reduces the friction. A check spring 
keeps the lever from moving too far, and pre¬ 
vents the platinum points from opening too 
wide when the magneto is driven at high 
speed. 

The current flows from the armature 
winding through the rod that is set in the 
shaft, and passes by the brushes to the in¬ 
sulated block N. Then it flows to switch con¬ 
tact B 2 by binding post A and the connect¬ 
ing wire. From this switch contact it may 
return to the armature by either of two 
paths; it may flow through the switch blade 
and the primary winding of the coil to mag- 


SECONDARY 

TERMINALS 



154 


Fig. 56.—Splitdorf Magneto Ignition System. 


















































TRANSFORMER MAGNETOS 155 


neto binding post 2, and by ground to the 
armature, or may flow through the switch 
blade and switch contact C to binding post 
3, insulated block M and to ground through 
the circuit breaker lever. This latter path is 
far easier for the current to flow in, and 
the current follows it as long as the platinum 
points are touching. When the points sep¬ 
arate, the current has no choice but to flow 
through the coil, and it is then that the spark 
is produced. 

The connections of the Remy magneto sys¬ 
tem are shown in Figure 57, and it will be 
seen that they differ from the Splitdorf con¬ 
nections in that the magneto current can 
flow through the primary winding of the coil 
only when the circuit breaker is closed. The 
core of the coil is thus magnetized by the 
flow of magneto current, and the sparking 
current is produced in the secondary wind¬ 
ing of the coil by the dying away of the mag¬ 
netism that occurs when the circuit breaker 
opens. The circuit breaker is arranged to 


SECONDARY 



156 


Fig. 57.—Principle of Remy Magneto. 


























































TRANSFORMER MAGNETOS 157 

open when the armature current is most in¬ 
tense, and when in consequence the core of 
the coil is strongly magnetized. 

In the Remy magneto, the winding is not 



built into the armature, as is the case in the 
magnetos that have been described, but is 
separate from the armature core. This 
winding is stationary; the part that revolves 
is the armature core, which is called the 
inductor, and it consists of a shaft with two 































































































































158 MOTOR CAR PRINCIPLES 


blocks of iron projecting from it, as shown 
in Figure 58. When these blocks are up and 
down, the magnetism can flow between the 
ends of the magneto,by way of the blocks. 
This corresponds to positions C and Gr. (Fig. 
40.) When the shaft revolves to bring the 
blocks crossways between the ends of the 
magnets, the magnetism will flow into one 
block, through the part of the shaft that is 
between the blocks, and through the second 
block to the other end of the magnet. This 
corresponds to positions A and E. (Fig. 40.) 

When the inductor is revolved, the part of 
the shaft lying between the blocks is alter¬ 
nately magnetized and demagnetized, and it 
is these changes in magnetism that produce 
currents in the winding. The coil of wire 
that forms the winding surrounds the part 
of the shaft that lies between the blocks, but 
does not touch it and does not revolve with 
it. One end of this coil leads to the insulated 
block of the circuit breaker, and the other is 
grounded. 


/ 



Fig. 59.—Remy Magneto Ignition System. 


159 





























































































160 MOTOR CAR PRINCIPLES 


One type of Remy magneto is shown in 
Figure 59, and the sketch also indicates the 
connections. One end, M, of the magneto 
winding is connected to one end of the pri¬ 
mary winding of the coil at binding post 1. 
The other end, O, is grounded at binding 
post 2. The remaining terminal of the pri¬ 
mary winding of the coil leads to magneto 
binding post 3, which is located on the in¬ 
sulated block of the circuit breaker. When 
the circuit breaker is closed, the current can 
flow across the platinum points B, to the 
lever D, to ground, to binding post 2, and so 
to the magneto winding. 

Figure 60 shows another type of Remy 
magneto, with a different construction of the 
circuit breaker. 


SPARK PLUG 



CIRCUIT BREAKER LEVER-^ SPRII 


Fig. 60.—Remy Magneto, Type R D. 

161 































CHAPTER X 


BATTEEY IGNITION SYSTEMS 


A MAGNETO can produce a current 
only when the armature is revolv¬ 
ing, and in order to start on the 
magneto the engine must be cranked quickly 
enough to revolve the armature at a suffi¬ 
cient speed to produce a sparking current. 
With small engines and good mixtures there 
is no difficulty in doing this, hut it may not 
be easy with large engines and imperfect 
mixtures. It is therefore quite usual for an 
engine to be fitted with an ignition system 
that will produce sparks regardless of 
whether the engine is running or at rest, in 
addition to the magneto. The current for 
such a system is obtained from a battery, 
which is made up either of dry cells or stor¬ 
age cells, the latter also being known as ac¬ 
cumulators. 


162 


BATTERY IGNITION SYSTEMS 163 


It lias been seen that a magneto produces 
a current by the rotation of the armature, 



Fig. 61. —Section of Dry Cell 

* 


for which power is required; the current is 
thus produced mechanically. A dry cell and 
a storage cell produce currents by the chem¬ 
ical action of some of the parts on the rest. 

A dry cell consists of a zinc cup, a stick of 






































































164 MOTOR CAR PRINCIPLES 


carbon, and a paste containing a chemical 
that under certain conditions will eat the 
zinc just as acid would eat it. The space be¬ 
tween the zinc cup and the stick of carbon is 
packed with the paste, but the carbon and 
the paste are prevented from touching the 
zinc by a lining of blotting paper. (Fig. 61.) 

A screw or nut attached to the stick of 
carbon, and another attached to the zinc cup, 
form the terminals; when they are connected 
to the circuit a current will flow from the 
carbon to the circuit, returning to the cell by 
the zinc. The moisture absorbed by the blot¬ 
ting paper and in the paste will form the con¬ 
ductor by which the current will flow from 
the zinc to the carbon, and complete its cir¬ 
cuit. 

No matter what the size of a dry cell may 
be, its current will have a working pressure 
of a little over one volt; a large cell, how¬ 
ever, will give a greater quantity of current 
than a small one. As an ignition system will 
usually require a pressure of six volts to 


BATTERY IGNITION SYSTEMS 165 


operate it, something must be done to bring 
the pressure up to this point. 

A crowd of people might be so dense that 
a man could not press bis way through, but 
if four or five men line up behind him, the 
pressure that they can exert in working to- 



Fig. 62 .—Cells Connected in Series. 


gether will gain them passage. Similarly, 
dry cells can be made to work together, and 
to give any pressure that may be required. 
To do this, the carbon terminal of one cell is 
connected to the zinc terminal of the next 
cell, as shown in Figure 62. The current 
from one cell must pass through the other 
cells in flowing over the circuit, and the volt¬ 
age will be increased as many times as there 
are cells. If each cell gives one volt, for ex¬ 
ample, five cells connected in this manner 


166 MOTOR CAR PRINCIPLES 


will give five volts. This is called connecting 

in series. 

While a dry cell may be capable of giving 
a considerable quantity of current, this can¬ 
not be taken from it all at once. For in¬ 
stance, if a crowd of people try to rush 
through a doorway, they will become 
jammed in it; they will be able to get 
through only by passing one at a time. A 
dry cell will act in a similar way, for while 
it can give a small current for a considerable 
time, it will become choked, so to speak, if a 
heavy current is taken from it. The flow of 
current will then cease entirely. The cell 
must be permitted to stand idle, and be given 
a chance to recuperate, before it will again 
be able to deliver a current. 

It is quite usual for an automobile to be 
supplied with five or six dry cells connected 
in series, but matters will be greatly im¬ 
proved if ten dry cells are used, connected as 
shown in Figure 63. The cells are divided 
into two groups of five cells each, the cells 


BATTERY IGNITION SYSTEMS 167 

of each group being connected in series; the 
free carbon terminals of each group are then 
connected together, and so are the free zinc 
terminals. Carbon and zinc are then con- 



Fig. 63. —Cells Connected in Series-Multiple. 


nected to the circuit in the usual manner. 
This is called connecting in series-multiple, 
or series-parallel. 

Ten cells connected in series-multiple will 
give a current at the same pressure as five 
cells connected in series, but will give a 
greater quantity of current; or what is more 
important, will give an equal quantity of 
current for a much longer time. Ten cells 



168 MOTOR CAR PRINCIPLES 


connected in series-multiple will last longer 
than ten cells used five at a time. 

A storage cell operates on a different prin¬ 
ciple, for when in a normal condition it is not 
capable of giving a current. If a current is 
passed through it, however, the parts of the 
cell undergo chemical changes, and become 
converted in composition. When given an 
opportunity they will then change back to 
their original condition, and in so doing will 
produce a current nearly equal to the current 
used in converting them. Electricity is not 
stored in a storage cell as water is stored in 
a tank; a storage cell might be compared 
with a spring that requires power to stretch 
it, and that delivers nearly equal power in 
snapping back to its normal form. 

A storage cell gives a current at a pressure 
of about two volts, and the quantity of cur¬ 
rent that it can deliver depends on its size; 
it is spoken of as having so-and-so-many 
ampere-hours capacity. An 80-ampere-hour 
cell is one that will give a current of one am- 


BATTERY IGNITION SYSTEMS 169 


pere for eighty hours, or a current of two 
amperes for forty hours, or a current of four 
amperes for twenty hours. A storage cell 
should be permitted to deliver only a small 
current; if it is short-circuited, the great 
rush of current will tend to heat it, and to 
injure or destroy it. 

When a storage battery is used, it is most 
advisable to secure an instruction book from 
the maker. This will give explicit directions 
for the use and care of the battery, and these 
directions should be scrupulously followed. 

All battery ignition systems operate by 
means of an induction coil, such as is de¬ 
scribed in the chapter on transformer mag¬ 
netos. The battery current flows through the 
primary winding of the coil and magnetizes 
the core; at the instant when the spark is 
required the battery circuit is broken, and 
the dying away of the magnetism produces 
a sparking current in the secondary winding. 

In addition to the battery and coil, the sys¬ 
tem must include a timer, which is a revolv- 


170 MOTOR CAR PRINCIPLES 


ing switch that controls the flow of battery 
current through the coil. 

In the Bosch battery system, the timer is 
a pivoted lever that makes and breaks the 



Fig. 64.—Action of Bosch Timer-distributor. 

f 


circuit; the cam that operates it has as many 
projections as the engine has cylinders. 
(Fig. 64.) Just before a piston reaches the 
firing point, the cam permits the platinum 
points to come together, and the battery cur¬ 
rent thereupon flows through the primary 
winding of the coil. At the instant when the 
















BATTERY IGNITION SYSTEMS 171 


spark is required, the cam moves the lever, 
thus separating the platinum points and 
breaking the circuit; a sparking current 
is then induced in the secondary winding 
of the coil, and it is deliv¬ 
ered to the proper cylin¬ 
der by the distribution 
that is built into the timer. 

The appearance of the 
Bosch timer-distributor is 
shown in Figure 65. This 
system produces a single 
spark, and a very intense 
one, at the instant when * @ 

the timer breaks the cir-FiG. 65.—Bosch Timer- 

distributor. 

CUlt. 

When starting a cold engine, it is fre¬ 
quently difficult to draw a proper mixture 
into the cylinder, and this is particularly 
true with the low grades of gasoline on the 
market. Under such conditions, ignition will 
be more sure if a shower of sparks is sent 
through the mixture instead of a single 






























172 MOTOR CAR PRINCIPLES 


spark; the first sparks heat up the surround¬ 
ing particles of mixture, which are then 
easily ignited by the following sparks. To 
produce this shower of sparks the coil is pro¬ 
vided with a device that makes and breaks 



Fig. 66.—Principle of Vibrator. 


the battery circuit a great number of times 
during the period when the timer contacts 
are open. 

This device is called the vibrator, and Fig¬ 
ure 66 shows the principle of its operation. 
It consists of a strip of iron supported at one 
end, and with the other end opposite one end 
of the core of the coil. When the core is mag- 













BATTERY IGNITION SYSTEMS 173 

netized it will attract to it the free end of the 
iron strip, or vibrator blade, as it is called. 
On the dying away of the magnetism, the 
free end of the blade will spring back to its 
original position. 

The connections are so made that the bat¬ 
tery current flows to a platinum tipped 
screw, thence to the blade when it is touch¬ 
ing the screw, and from the blade to the 
winding of the coil. When the core becomes 
magnetized, it draws the blade away from 
the screw, and this movement breaks the cir¬ 
cuit; the consequent dying out of the mag¬ 
netism of the core induces a sparking cur¬ 
rent in the secondary winding, and at the 
same time permits the blade to spring back 
into contact with the screw. The vibrator 
moves hundreds of times a second, and a cor¬ 
responding number of sparks is produced. 

In the Bosch coil, the parts of which are 
shown in Figure 67, the vibrator is set in ac¬ 
tion by pressing the button in the end plate 
of the coil housing; when the button is 


174 MOTOR CAR PRINCIPLES 


pressed in and turned to the right, the vibra¬ 
tor is maintained in action. The vibrator 
should be used only in starting the engine; 
when the engine is running the button should 
be released. 

In many battery systems the vibrator is 



Fig. 67.—Bosch Coil. 


permanently in circuit, and a shower of 
sparks is produced whenever the timer 
makes contact. The first of these sparks ig¬ 
nites the mixture; by the time that the rest 
of them pass the mixture is ignited, and they 
are therefore wasted. Furthermore, the con¬ 
stant movement of the vibrator blade causes 
the rapid wear of the platinum points; for 


ADJUSTING SCREW 



175 


Fig. 68.—Principle of Battery Ignition System. 







































































































































































176 MOTOR CAR PRINCIPLES 


these reasons the use of a vibrator coil is 
dying out. 

The principle of the vibrator coil ignition 
system is shown in Figure 68. The timer 
consists of a ring of insulating material, with 
metal plates set in it, one for each cylinder; 
the diagram shows a single cylinder timer. 
The connections between the battery, coil, 
vibrator and timer. contact plate are indi¬ 
cated; the remaining terminal of the battery 
is grounded, and as the revolving brush is 
attached to a shaft driven by the engine, it 
is grounded also. The circuit is consequently 
closed when the brush touches the contact 
plate. 

In vibrator coil systems, it is frequently 
the case that each cylinder has its own coil. 
Figure 69 shows the connections for a two- 
cylinder horizontal engine; the coil box con¬ 
tains two complete and independent coils, 
and the timer has two contact plates, one for 
each coil. At the instant when one of the 
pistons reaches the firing position, the timer 


BATTERY IGNITION SYSTEMS 177 

will make contact with one of the coils, and 
the sparking current that is then produced 
will be led to the proper spark plug. 



Fig. 69.—Connections of Two-cylinder Battery System. 


Figure 70 shows the connections of a four- 
cylinder system. The coil box contains four 



























































































PRIMARV TCRrtlNALS TO TIMCR^^ 



178 


Fig. 70.—Connections of Four-cylinder Battery System. 




































































































BATTERY IGNITION SYSTEMS 179 


coils, and the timer lias four contacts. It 
will be noticed that the secondary terminals 
of the coils are connected to the spark plugs 
in a regular manner; that is, the left hand 
coil is connected to plug No. 1, the second 
coil from the left is connected to plug No. 
2, and so on. The firing order of the engine 
is either 1, 2, 4, 3, or 1, 3, 4, 2, and the pri¬ 
mary windings of the coils must be con¬ 
nected to the timer in such a manner that 
the sparks will be produced in corresponding 
order. 

The timer is shown in contact with the 
connection to coil No. 1. Turning in the di¬ 
rection of the arrow, it will next make con¬ 
tact with the connection of coil No. 3; coil 
No. 4 will then be brought into circuit and 
then coil No. 2. This is done by the manner 
in which the primary windings of the coils 
are connected to the timer. 

Figure 71 shows a cross-section of a coil, 
with its connections to the battery, the timer 
and the spark plug. 



Fig. 71.—Vibrator Coil and Engine. 

180 









































































































































BATTERY IGNITION SYSTEMS 181 


In such a system as this, each coil has its 
own vibrator, and the adjustment of these 
vibrators so that the coils will all act alike 
is not an easy matter. Figure 72 illustrates 
what is known as the master vibrator sys¬ 
tem, in which only one vibrator is used for 
the entire set of coils. By studying the dia¬ 
gram it will be seen that the vibrator is con¬ 
nected to one terminal of the primary wind¬ 
ing of each coil; the other terminals of the 
primary windings lead to the timer contacts 
according to the firing order of the engine. 
By this arrangement the coils act in a uni¬ 
form manner. 

Vibrator coils are frequently used with a 
combined timer and distributor, similar in 
arrangement to the Bosch timer-distributor 
that has been described. The connections of 
such a system are shown in Figure 73. The 
timer has four contacts, but these are con¬ 
nected to the primary winding of the single 
coil; the battery current will thus flow 
through this winding whenever the timer 



182 


Fig. 72.—Master Vibrator Battery System. 
























































BATTERY IGNITION SYSTEMS 183 

brush touches one of the contacts. The sec¬ 
ondary terminal of the coil leads to the re¬ 
volving distributor brush, and the sparking 
current is thus passed to the proper spark 
plug. The illustration shows the parts of 
the timer-distributor as being separated, 
but in the actual apparatus they are close 
together, and inclosed in a dust-proof hous¬ 
ing. 

In the Delco ignition system a vibrator coil 
is used, but a device is provided that per¬ 
mits the vibrator to make only one move¬ 
ment. By this means the quantity of battery 
current used is reduced. 

The Atwater Kent system secures a reduc¬ 
tion in battery consumption by an extremely 
brief closing of the battery circuit. This is 
done by mechanical means, and the move¬ 
ment of the contact blade is so rapid that it 
cannot be observed. The period during 
which the primary circuit is closed is so brief 
that the core of the coil cannot become thor¬ 
oughly magnetized; the spark is due to the 



184 











































































BATTERY IGNITION SYSTEMS 185 


extreme abruptness with which the circuit 
is broken, and the correspondingly abrupt 
dying away of such magnetism as has been 
produced. 


CHAPTER XI 


COMBINED MAGNETO AND BATTERY SYSTEMS 


W HILE a magneto is considered to 
be the best generator of an igni¬ 
tion spark, it is capable of giv¬ 
ing a sparking current only when the arma¬ 
ture is revolving. It is therefore customary 
to add to the engine equipment a battery sys¬ 
tem that will produce a sparking current at 
slow cranking speed, or when the engine is 
at rest. 

Some automobile makers believe that if a 
second ignition system is provided, it should 
be so complete that it can be used in case the 
magneto should cease to give service, and 
they arrange the engine with a drive for a 
timer or a timer-distributor in addition to 
the magneto drive, and place two spark plugs 
in each cylinder; one for the magneto and 
one for the battery system. 

186 


COMBINATION SYSTEMS 


187 


The Bosch battery system is used for the 
battery side of such an arrangement, and the 
manner in which the connections are made 
is shown in Figure 74. The switch, which is 



Fig. 74.—Connections of Bosch ‘ 1 2-independent *' 

System. 


combined with the coil, permits the engine 
to be run on the magneto alone, on the bat¬ 
tery system alone, or on both battery and 
magneto, in which case both sets of spark 
plugs will operate. 

In order to simplify the construction of 







































































































188 MOTOR CAR PRINCIPLES 

the engine, the parts of the battery system 
are frequently combined with the magneto to 



13 42 4 


Fig. 75. —Bosch Dual Magneto. 

form a dual system. The Bosch dual ignition 
system consists of a standard direct high 
tension magneto, to which are added parts 









COMBINATION SYSTEMS 189 


that are practically identical with the parts 
of the Bosch battery system. 

Figure 75 shows an end view of a Bosch 
dual magneto. The magneto circuit breaker 
will be seen to be identical with the circuit 
breaker of the standard magneto, except that 
a steel cam with two projections is at¬ 
tached to the disk that carries the circuit 
breaker parts. The cam bears the number 

43. A lever, 13, is pivoted on the magneto 

* 

in such a position that its end is struck by 
the cam in revolving. The lever is thus 
caused to move on its pivot, and the plat¬ 
inum point that it carries is separated from 
the platinum tip of screw 4. 

Screw 4 is insulated, and is connected to 
the battery system by binding post 42. The 
lever is grounded, and in consequence the 
battery circuit is closed through the primary 
winding of the coil when the lever touches 
thb screw. 

In the independent Bosch magneto the 
sparking current passes from the slip ring 


190 MOTOR CAR PRINCIPLES 


directly to the distributor by an internal con¬ 
nection. In the dual magneto the distributor 
is used for the sparking current of the coil 
as well as for the sparking current generated 



Fig. 76. —Connections of Bosch Dual System. 


by the magneto, and as these two currents 
cannot be flowing to the distributor at the 
same time, this internal connection is done 
away with. As shown in the wiring diagram 
of the system, Figure 76, the magneto slip 
ring, 3, is connected to switch terminal 3, 
and switch terminal 4 is connected to a bind- 







































































































COMBINATION SYSTEMS 191 


ing post in the center of the distributor plate. 
When the engine is running on the magneto, 
the magneto current flows from the slip ring 
to the switch, and from there to the dis¬ 
tributor. When the switch is in the battery 
position the magneto is cut out of circuit, 
and it is then the sparking current from the 
coil that flows over wire 4 to the distribu¬ 
tor. 

With the exception of the distributor and 
the spark plugs, the two systems are abso¬ 
lutely independent of each other. 

A dual magneto can be converted to inde¬ 
pendent form by connecting slip ring ter¬ 
minal 3 to distributor terminal 4, using a 
heavily insulated wire. This will permit the 
engine to be run on the magneto, even with 
the coil removed from the car. 

With the engine at rest and the switch in 
the battery position, the pressing of the but¬ 
ton in the center of the switch plate will pro¬ 
duce a vibrator spark that will be passed by 
the distributor to the proper cylinder; if the 



Fig. 77.—Bosch Dual Coil. 


TdSAtM hues 

ft CAMS ST Tb second Sei 

Inl et Val ves otJman Plugs 


Bosch Two Point Switch 




GROUND 


Switch Positions 
/* Magneto Operating Set op Spark 
Plugs nearest Inlet halves 

2- Magneto Operating Both Sets of 
Shirk Plugs 


heavy l/nes Indicate Hi6h tension Cables 


Bosch Dual Coil 



\tAinnA * gaounc 


Fig. 78. —Connections of Bosch Two-spark Dual 

System. 


192 







































































































COMBINATION SYSTEMS 193 


cylinder contains gas, ignition will occur and 
the engine will start. 

Figure 77 shows a cross section of the coil 
and the arrangement of the vibrator. When 
button 4 is pressed, its end comes into con¬ 
tact with spring 13, and closes the battery 
circuit through the primary winding; vibra¬ 
tor blade 14 will then operate. 

The engine may be run on the battery sys¬ 
tem continuously, but the press button 
should be turned to the word “ run a sin¬ 
gle contact spark will then be produced. The 
button should be turned to the word 
“ start ” only when a vibrator spark is re¬ 
quired, as will be necessary when starting 
an engine on a poor mixture or in cold 
weather. 

The connections of the Bosch 2-spark dual 
magneto are shown in Figure 78. 

The Z R types of Bosch single and 2-spark 
magnetos are connected in a similar manner, 
except that switch terminal 4 leads to the 
shaft end of the magneto, from which point 


TO SPARK PLUGS 




194 


CIRCUIT BREAKER 

Fig. 79.—Principle of Splitdorf Dual System. 


























































































COMBINATION SYSTEMS 195 


an internal connection leads the sparking 
current to the distributor. 

In the Splitdorf and Remy dual systems 
the magneto current and the battery current 
are transformed in the same coil and timed 
by the same timer. 

The connections of the Splitdorf mag¬ 
neto are shown in Figure 79. With the 
switch blade in the position shown, the mag¬ 
neto will operate in the usual manner. When 
the switch blade is turned to connect switch 
terminals 3 and 4, the magneto will be cut 
out of circuit, and the battery will be thrown 
into circuit with the coil and the circuit 
breaker. When the engine stops with the 
magneto circuit breaker open, the pressing 
of the press button will close the circuit, and 
on releasing it a spark will be produced. 

Figure 80 shows the connections of the 
Remy dual system, the action of which is 
similar to the action of the Splitdorf dual 
system. 

In the Bosch duplex system a different 


SECONDARY TO DISTRIBUTOR 




X 


4 \ 


X 


< 


\. 


196 


Fig. 80.—Principle of Remy Dual System. 





















































COMBINATION SYSTEMS 197 


principle is used. The battery current is per¬ 
mitted to flow through the primary winding 
of the armature in such a manner as to sup¬ 
plement such magneto current as is pro¬ 
duced at low speeds; or if the magneto is at 
rest, the armature transforms the battery 



Fig. 81. —Principle of Bosch Dual System. 


current just as a coil would do it. The prin¬ 
ciple is shown in Figure 81. 

The magneto is identical in every way 
with the independent magneto, except that 
two half-rings of brass, called segments, 
are attached to the inside of the circuit 
breaker cover, and that the circuit breaker is 















198 MOTOR CAR PRINCIPLES 


provided with two carbon brushes. One 
brush, A, is set in the insulated block of the 
circuit breaker, while the other, B, is lo¬ 
cated on .the circuit breaker disk and is 
therefore grounded. When the cover is in 
position the brushes are in contact with the 
segments. 

One terminal of the battery leads to a 
small coil that has only a few layers of coarse 
wire; this coil acts like a valve in permitting 
only a small current to pass through it. 
From the coil a wire leads to one of the seg¬ 
ments, while the other segment is connected 
to the remaining battery terminal. 

With the circuit breaker in the position 
shown, and the cover in place, brush B will 
touch segment 1, and brush A will touch seg¬ 
ment 2. The circuit breaker being closed, 
the battery circuit will be complete, for the 
current can flow from segment 1 and brush 
B to ground, across the platinum points, and 
back to the battery by brush A and segment 
2. If the armature is turned a trifle, so that 


COMBINATION SYSTEMS 199 


the circuit breaker is open, there will still be 
a circuit, for the current can then flow from 
brush B and ground to the grounded end of 
the armature winding, through the primary 
winding to the insulated block, and back by 
brush A as before. 

If the armature is at rest with the circuit 
breaker open, which will be the case with an 
engine in good condition, the battery circuit 
may be broken by a press button, and a 
sparking current will be produced in the sec¬ 
ondary winding. 

When the armature revolves slowly, as is 
the case when the engine is cranked, the sud¬ 
den rush of battery current through the pri¬ 
mary winding at the instant when the 
circuit breaker opens will supplement 
and strengthen the magneto current, with 
the result that a very intense spark is 
produced. 

When the engine is running, the armature 
will be moving fast enough to produce its 
own spark; the effect will then be to choke 


200 MOTOR CAR PRINCIPLES 


the battery current, so to speak, and the con¬ 
sumption will be little or nothing. 

The current from a battery flows constantly 
in one direction, and is known as a direct 
current. A magneto, on the other hand, gives 
what is called an alternating current, for dur¬ 
ing one-half of the revolution the current 
will flow in one direction, and will flow in 
the opposite direction during the other half 
of the revolution. If the battery and magneto 
circuits are connected, the currents will 
thus supplement each other during one-half 
of the revolution, and oppose each other dur¬ 
ing the other half, unless measures are taken 
to send them in similar directions all the 
time. In the duplex magneto this is done by 
the segments on the circuit breaker cover, 
which form a commutator. 

During one-half of the revolution of the 
armature, the magneto current flows from 
the insulated block across the platinum 
points to the lever, and during the other half 
it flows from the lever across the platinum 


COMBINATION SYSTEMS 201 

points to the insulated block. Inasmuch as 
the cover is stationary, it can be seen that 
during one-half of the revolution carbon 
brush A is touching segment 2 and carbon 



Fig. 82 .—Connections of Bosch Duplex System. 


brush B is touching segment 1, and that dur¬ 
ing the other half-revolution brush A will be 
touching segment 1 and brush B segment 2. 
As the battery current flows constantly to 
one of the segments, No. 1, for instance, it 
will flow from that segment to brush A dur¬ 
ing half of the revolution, and to brush B 
during the other half. The segments thus 














































202 MOTOR CAR PRINCIPLES 


keep the battery current in step with the 
changes in the flow of magneto current. 

The connections of the duplex system are 
shown in Figure 82, and they must be fol¬ 
lowed exactly. If the battery connections 
are reversed, the battery current will oppose 
the magneto current instead of supplementing 
it, and no sparks will be produced. With re¬ 
versed connections, a spark can be produced 
by the press button when the magneto is at 
rest, for then there is no magneto current to 
oppose the battery current. The engine may 
start on the spark, but will not continue to 
run; this condition is an indication that the 
battery connections are reversed. 


CHAPTER Xn 


SPARK PLUGS, CABLES, TERMINALS, AND 

COUPLINGS 


I N order that a spark may be formed, the 
circuit provided for the sparking cur¬ 
rent must include an air space; the size 
of this space should be such that the pressure 
will force the current across it. This space 
is located in what is known as the spark 
plug. 

The spark plug is formed of two pieces of 
metal, the ends of which are brought suffi¬ 
ciently close together to form the proper gap. 
These two pieces of metal or electrodes are 
held in position and are prevented from 
touching by some form of insulating ma¬ 
terial. 

An illustration of a spark plug, together 
with a section showing its interior construc¬ 
tion, is indicated in Figure 83. The outer 

203 


204 MOTOR CAR PRINCIPLES 


part or shell is made of metal, and is pro¬ 
vided with a screw thread that permits it to 



Fig. 83.—Spark Plug. 


be screwed into an opening in the cylinder. 
Within the shell is the insulator, and 



































































































PLUGS, CABLES, TERMINALS 205 

through the center of this passes the second 
or center electrode, which terminates at one 
end with a binding nut, at which is made the 
connection with the sparking circuit. The 
current passes from the center electrode to 
the shell, which forms the outer electrode, or 
from the shell to the center electrode. The 
outer shell being in contact with the metal of 
the engine, the current can pass from one to 
the other, and thus to ground. 

The insulator is subjected to the intense 
heat and pressure existing in the cylinder, 
and must be of a material that will resist in¬ 
juries from these causes. The most satisfac¬ 
tory insulating material is a composition 
known as steatite, because in addition to its 
other advantages it is practically unbreak¬ 
able. Porcelain and mica are also very fre¬ 
quently used. 

An electric current will find it easier to 
pass between two pointed pieces of metal 
than between round or flat ends. Spark 
plugs constructed in this manner will have 


206 MOTOR CAR PRINCIPLES 


an advantage over those of which the elec¬ 
trode ends are flat or rounded in permitting 
the current to pass at lower pressure; an en¬ 
gine may thus be started at a lower crank¬ 
ing speed on the magneto than will be pos¬ 
sible when the electrodes are blunt. A so- 
called electric spark is in reality not visible 
electricity, but is composed of tiny particles 
of metal torn off and vaporized by the in¬ 
tense heat of the current. The electrodes of 
a spark plug will thus burn away in time, 
and the gap will be increased. It has been 
found that nickel or its alloys will permit 
the formation of a good spark, while at the 
same time they will resist the burning effect 
longer than any other material that it is 
practical to use. 

The parts of a spark plug should be assem¬ 
bled in such a manner as to prevent the pos¬ 
sibility of leakage of compression. When the 
parts of a spark plug are screwed together 
they should be inspected at frequent inter¬ 
vals to guard against this. 


PLUGS, CABLES, TERMINALS 207 

The gap provided between the electrodes 
will vary from 1-50 inch to 1-32 inch, accord¬ 
ing to the characteristics of the engine. A 
wide gap presents more resistance to the 



Fig. 84.—Correct Location of Spark Plug. 


passage of the current than a small one, and 
if it is difficult to start an engine on the mag¬ 
neto the cause will frequently be located as 
lying in too great a spark plug gap. 

It is almost invariably the case that the 
spark plug is set in the cap of the inlet valve 
or as close in the inlet valve as possible, in 
order that the spark plug points may be sur- 


























208 MOTOR CAR PRINCIPLES 


rounded by fresh mixture. A spark plug lo¬ 
cated in the exhaust valve cap of a T-head 
engine may cause misfiring because the fresh 
mixture does not reach it. 



Fig. 85. —Pocketed Spark Plug. 


The spark plug should be so located that 
the sparking points are actually plunged into 
the mixture, as indicated in Figure 84. If 
the valve cap is so thick that the spark plug 
points do not project, as is indicated in Fig¬ 
ure 85, the cavity or pocket will contain a 
mixture of fresh and burnt gases. Under 

































PLUGS, CABLES, TERMINALS 209 

such conditions a greater advance will be re¬ 
quired than is justified by the engine size, be¬ 
cause of the slowness with which the flame 
that starts at the 
spark plug will reach 
the main body of mix¬ 
ture. When such a 
condition exists, the 
running of the engine 
will be greatly in¬ 
creased by drilling out 
the valve cap to per¬ 
mit the spark plug to 
be inserted in it 
deeper, as shown in 
Figure 84. Fig * 86 

In many engines the 
spark plug passes through the cylinder head 
or wall, which is of considerable thickness. 
A condition of this sort cannot be remedied 
by the user of the engine, and in order to 
plunge the sparking points into the fresh 
mixture it will be necessary to use a spark 



Extended Spark 
Plug. 











































210 MOTOR CAR PRINCIPLES 


plug made with an extension below the 
threaded portion, as shown in Figure 86. 
The results from this are not altogether satis- 



Fig. 87. —Correct Location of Spark Plug. 

factory, because the heat absorbed by the ex¬ 
tended end of the plug cannot pass off to the 
water jacket sufficiently rapidly, and over¬ 
heating is liable to result. The effect of this 
will be the warping of the central electrode 
and a consequent alteration in the size of the 
spark gap; or if the sparking points are slen- 



































PLUGS, CABLES, TERMINALS 211 

der they will become incandescent and will 
ignite the incoming fresh mixture before the 
spark passes. 

A properly placed spark plug for such an 
engine is indicated in Figure 87. In this case 
the opening has been made of sufficient size 
to permit the spark plug to be set into it far 
enough to allow the sparking points to come 
into contact with the mixture. 

It is poor economy to invest in a badly 
constructed and inefficient spark plug. The 
cost of a high-grade plug is not excessive, 
and its use will render the engine more effi¬ 
cient and reliable. 

Cables of two sizes are in use on an igni¬ 
tion system, one, the low-tension cable, being 
comparatively lightly insulated because it 
carries the low-pressure current from the 
battery or from the primary circuit of the 
magneto, while the other, the high-tension 
cable, conducts the sparking current from 
the distributor to the spark plug. 

The insulation of the high-tension cable 


212 MOTOR CAR PRINCIPLES 


must be of such quality and thickness that it 
will be easier for the current to make its cir¬ 
cuit through the spark plugs than to break 
through the insulation, and thus make a new 
circuit for itself. 

In a high-tension cable soft rubber of the 
best quality will give better satisfaction than 
any other. A cable with very thick insula¬ 
tion will retain the current, but it will be 
likely to produce a condition that will inter¬ 
fere with the operation of the engine. 

Everyone has experienced the electrifying 
of a hard rubber comb when combing the 
hair on a cold morning; the passage of a 
high-tension current, particularly that pro¬ 
duced by a true high-tension magneto, will 
have a similar effect upon the insulation of 
the cable through which it passes. The re¬ 
sult will be what may be termed a static 
charge on the surface of the insulation; when 
the charge becomes sufficiently intense, the 
electricity thus collected will pass to ground. 
The thicker the insulation the greater will be 


PLUGS, CABLES, TERMINALS 213 


its surface, and consequently the greater will 
be the opportunity for the collection of the 
charge. 

If the cable is held in metal supports, 
which are attached directly to the engine, 
this charge will pass off to ground without 
having any effect, but if the cables are led 
through a tube made of fiber or other insulat¬ 
ing material, as is frequently the case, this 
charge will go to ground across the elec¬ 
trodes of the spark plug, forming a spark as 
it passes. This second spark will normally 
follow the passage of the ignition spark and 
will do no harm. 

When the cables are long, so that the sur¬ 
face is considerable, the insulation may be¬ 
come so highly charged that the electricity 
will pass across the electrodes of the spark 
plug before the ignition spark passes. It 
will then cause the preignition of the charge 
and result in backfiring. 

The most satisfactory results will be at¬ 
tained when the ignition cables are short, 


214 MOTOR CAR PRINCIPLES 


and when they are supported in such a way 
that the electricity collecting on the surface 
of the cable insulation may pass directly to 
the metal of the engine. This is assured by 
supporting the cables in metal cleats. The 
discharge of this electrical charge is fre¬ 
quently mistaken for defective insulation. 

The end of the cables should always be 
provided with metal terminals. When the 
insulation is stripped from the wire and the 
wire strands are twisted together and then 
applied to a binding post, there is great lia¬ 
bility that a stray strand of the wire will per¬ 
mit a short circuit to some neighboring piece 
of metal. The use of a terminal not only pre¬ 
vents this, but protects the cable from break¬ 
ing at the point where the wire emerges 
from the insulation. 

It is frequently the case that the magneto 
is driven through some form of coupling or 
universal joint. With quiet running modern 
engines the magneto is frequently blamed for 
making a noise that in fact originates in the 


PLUGS, CABLES, TERMINALS 215 

coupling. A coupling may feel tight and 
may appear to have no lost motion, but may 
nevertheless be the cause of an annoying rat¬ 
tle. At certain points in its revolution a 
magneto requires more power to turn the 
armature than is necessary at other points, 
because of the constant change in the flow 
of magnetism. This has the effect of check¬ 
ing the rotation of the armature twice in 
each revolution, and this intermittent resist¬ 
ance to turning will cause a rattle in the 
coupling unless it is constructed in such a 
manner that a spring action absorbs the lost 
motion. 


CHAPTER Xin 


TRANSMISSION 


T HE transmission of an automobile 
consists of those parts that transmit 
to the driving wheels the power de¬ 
veloped by the engine. 


THE CLUTCH 

Because a gasoline engine must be in oper¬ 
ation before it can deliver power, a clutch is 
provided by means of which it may run free 
or be so connected that it drives the car, one 
of its two chief parts being attached to the 
engine and the other to the transmission. 
When the two parts are in contact, the trans¬ 
mission is driven, and when separated, the 
engine and transmission are independent of 
each other, and may be stationary or in mo¬ 
tion. A clutch must be of such a nature that 
it does not apply the power of the engine in- 

216 


TRANSMISSION 


217 


stantly, but gradually, so that the car starts 
slowly and without jerking. If the power 
were to be applied suddenly, the effort of 
starting the stationary car would either over¬ 
come the momentum of the engine and stop 
it, or would jerk the car into such sudden 
motion that it might be badly wrenched. By 
making the clutch so that it is permitted to 
slip when first applied, the part that is 
driven is gradually brought to the speed of 
the part that drives, when slipping ceases 
and the two make firm contact. 

The most usual form of clutch is the fric¬ 
tion cone, in which the fly wheel of the en¬ 
gine is utilized as the driving part, the rim 
being broad and thick, with its inner side 
funnel-shaped, or beveled. A metal cone that 
fits the bevel is carried on the end of a shaft 
of the transmission, the shaft at this point 
being square, to fit a square hole in the hub 
of the cone. This arrangement permits the 
cone to slide along the shaft while always 
revolving with it. When the cone is pressed 


218 MOTOR CAR PRINCIPLES 


to a seat in the fly wheel, which is accom¬ 
plished by means of a heavy coil spring, the 
friction between its leather-covered surface 
and the surface of the fly wheel causes the 
two parts to revolve together, and by its fit 
on the square shaft the transmission is set 
in motion, and through that the car. The 
clutch is thrown out of contact by means of 
a foot pedal that acts on a ring fitting in a 
groove around the hub of the cone; when the 
pedal is released, the spring forces the cone 
to its seat (Fig. 88). In order to support it, 
the end of the shaft carrying the cone pro¬ 
jects into the hub of the fly wheel, where it 
rests in a bearing, this arrangement in no 
manner preventing the two parts from acting 
independently of each other. 

In the reversed type of friction-cone clutch 
a funnel-shaped ring is bolted to the rim of 
the fly wheel and forms the seat, the cone fit¬ 
ting inside of it (Fig. 88). Depressing the 
pedal moves the cone toward the fly wheel 
instead of away from it, as in the regular 


TRANSMISSION 


219 


type, and while there is no difference in the 
effect of one as against the other, the re¬ 
versed type is more compact. 

The multiple-disk clutch, which is rapidly 
coming into use, depends on the friction be¬ 
tween the flat surfaces of metal when pressed 
together. An experiment illustrating this is 
to place a silver dollar between two half dol¬ 
lars, and to press them together between 
the thumb and finger. It will be found 
that a light pressure is sufficient to pro¬ 
duce friction that will make it difficult to 
revolve the large coin between the smaller 
ones. 

The parts of a simple form of multiple- 
disk clutch, as shown in Figure 89, are a 
flange on the engine shaft, a smaller flange 
with a square-hole, square-shaft arrangement 
on the transmission shaft, and large and 
small rings placed alternately. The large 
rings are driven by the large flange, fitting 
loosely on pins, or studs, projecting from it, 
and the small rings are similarly attached to 



THROW M 


THROW OUT 

Eft/CT/Off COffE CLUTCH 



flt wueti 


UATHen ON CONI 
friction cons 


sea ring — 
fo« c nance 
SPeeo COH SHAFT 


emu rtf 

•SHAFT' 



CRAMCe SFee/> 
C(AH SHAFT 

SPHlNC 


Pin BOL-rtO To til »urtc 


THROWN IN 


THROWN OUT 

ftE/ERSED FRICTION CONE CLUTCH 

Fig. 88.—Friction Cone Clutches. 

220 














































































































































































TRANSMISSION 


221 


the transmission shaft. The openings in the 
large or driving rings are large enough to 
contain the studs carrying the small rings, 
so that when the parts are assembled the 
outer surfaces of the small or driven rings 
are in contact with the inner surfaces of the 
driving rings. A heavy coil spring is ar¬ 
ranged to press the small flange toward the 
flange on the engine shaft, binding the rings 
that it carries between the driving rings, 
and the latter are often faced with leather 
to increase the friction between them. When 
the small flange is released from the pressure 
of the spring by depressing the pedal, the 
driving and driven flanges with their rings 
are independent of each other, and the en¬ 
gine may run free while the transmission 
shaft is stationary or revolving. A clutch of 
this type is incased and runs in oil, which 
prevents the rings from gripping suddenly; 
when the pressure of the spring is applied, 
the oil is gradually squeezed out from be¬ 
tween them, and the slipping of the driving 


6TVOS for omrcrt tvrttt 



flanse an charge shed 

CeAH SHAFT 


■A \Jh/} \^A 

PARTS OF mm PIE DISC CLUTCH 


ruut6£ a» (none 3Mf>n 


A- LEATHER FACEO OAIUHIC FhRCi 
Q ' OAJ HER 01RCS 


Cm a nee speed 

(EAR SHAFT 



—end re 


SHAFT 


multiple o/sc clutch assembled 

Fig. 89.—Multiple Disk Clutch. 


222 








































































































































































TRANSMISSION 


223 


and driven rings is reduced as they are 
forced into contact. 

An internal-expanding clutch consists of a 
broad ring, or drum, against the inner sur¬ 
face of which are two pieces of metal 
shaped to fit. The pieces of metal, or shoes, 
are pivoted together at one end so that they 
may be moved in or out, after the manner 
of the handles of a pair of scissors; when 
open they bear against the inside surface of 
the drum, and when closed they are free 
from it. The drum is attached to the engine 
shaft and the shoes to the transmission 
shaft, the friction between them being so 
great that the transmission shaft is carried 
around as the drum revolves. The shoes are 
kept in contact with the drum by a coil 
spring, the depression of a pedal releasing 
them from its pressure. 

CHANGE-SPEED MECHANISM 

The change-speed mechanism, to which the 
clutch transmits the power of the engine, is 


224 MOTOR CAR PRINCIPLES 


to the engine what a block and tackle is to a 
man who lifts a heavy weight, and is neces¬ 
sary because of the varying resistance to the 
movement of the car in traversing steep, 
rough hills and smooth avenues. A change- 
speed mechanism may be defined as an ar¬ 
rangement by which the relative number of 
revolutions of the crank shaft and driving 
wheels may be altered to suit conditions. If 
the driving wheels revolve but once while the 
crank shaft makes twelve revolutions, the 
car will move at one sixth the speed that it 
would have if the wheels revolved once to 
every two revolutions of the crank shaft, but 
it will have six times the ability to overcome 
the resistance presented by a hill or sandy 
road. 

If a gasoline engine were so connected that 
the relative number of revolutions of the 
crank shaft and wheels could not be changed, 
a slowing down of the car through the re¬ 
sistance presented by a rough hill would 
slow the engine to correspond, and as speed 


TRANSMISSION 


225 


is an important factor in the power that the 
engine delivers, it would be prevented from 
doing the work of which it is capable at the 
time when it was most necessary. By means 
of the change-speed mechanisms in most 
general use, the number of revolutions of the 
crank shaft to one of the wheels may be from 
two to eighteen, the former giving the car 
high speed over a smooth road, and the latter 
slow speed, but greater ability to overcome 
hills and heavy roads. 

To attain this result, gears are used. If 
two gears having the same number of teeth 
are in mesh, they will make the same num¬ 
ber of revolutions, and the force with which 
the driven gear will revolve will be the same 
as that of the driving gear, less the friction 
of the teeth. If the driven gear has twice 
the number of teeth of the driving gear, it 
will revolve at half the speed, but with twice 
the force. 

The forms of change-speed mechanism 
most largely used are based on this principle, 


226 MOTOR CAR PRINCIPLES 


which is so applied that the gear driven by 
the engine may be in mesh with a gear that 
has many more teeth and revolves much 
slower in consequence, or a gear that has pos¬ 
sibly one and a half times the number of 
teeth, or a gear that has the same number of 
teeth, and therefore revolves at the same 
speed. The sliding-gear mechanism takes its 
name from the arrangement by which the 
changes in the combination of gears are ef¬ 
fected by sliding them along a shaft, to 
mesh with other gears on a shaft driven by 
the engine. 

The driver changes the gears by moving a 
lever that in the progressive type moves for¬ 
ward by degrees to move the car on the slow 
speed, the intermediate speeds, and the high. 
A typical arrangement of the progressive 
type of sliding change-speed mechanism is 
shown in Figure 90. The power of the en¬ 
gine is transmitted to a short, hollow shaft, 
called a sleeve (A), which carries a gear 
(B) that is in permanent mesh with a gear 



F IG< 90.— Sliding Gear—Progressive Type. A, sleeve driven by 
engine; B, gear on sleeve; C, gear on countershaft; D, low-speed 
gears; E, second-speed gears; F, idler for reverse; G, clutch for 
high speed; H, connected to rear wheels; J, gears sliding on 
square shaft. 


227 









































































































































































































































































































228 MOTOR CAR PRINCIPLES 


(C) on the end of the counter-shaft. Paral¬ 
lel to the countershaft is another shaft, one 
end of which is held in a bearing in the hol¬ 
low sleeve; while the sleeve supports this 
shaft, the two may revolve independently of 
each other. The second shaft is square, or 
of such a construction that while the two 
gears that it carries may slide along, they re¬ 
volve with it. The gears on the square shaft 
are of different sizes, and in sliding on it 
come successively into mesh with gears car¬ 
ried on the countershaft. Because of the 
gears between them, the countershaft re¬ 
volves when the engine revolves the sleeve; 
but the speed of the square shaft depends on 
the combination of gears in mesh between it 
and the countershaft. When the sliding 
gears are in such a position that they are not 
in mesh with the countershaft gears, the 
square shaft is independent of the counter¬ 
shaft, and may revolve or be stationary, the 
gears then being in the neutral position. 
When the sliding part is moved so that its 


TRANSMISSION 


229 


largest gear is in mesh with the smallest of 
the countershaft gears (D), the square shaft 
will revolve at a slower speed than the coun¬ 
tershaft, because its gear is larger than the 
one driving it. Again sliding the moving 
part will separate these gears, and bring the 
next pair (E) into mesh, the square shaft 
then moving at a higher speed, but still 
slower than the countershaft because of the 
difference in the size of the gears. Sliding 
the moving part still farther along the shaft 
will disengage the second-speed gears and 
engage the high speed, in which the square 
shaft revolves at the speed of the sleeve and 
crank shaft, this being effected by locking 
the moving part to the sleeve by means of 
a clutch (G). This clutch consists of several 
fingers projecting from the moving part, cor¬ 
responding to the spaces between similar fin¬ 
gers on the end of the sleeve. The locking 
together of the square shaft and sleeve gives 
what is known as the direct drive, which is 
of comparatively recent development; some 


230 MOTOR CAR PRINCIPLES 


designs of sliding gears still use a third pair 
of gears which, being of the same size, give 
the square shaft the speed of the crank shaft. 
By the use of the direct drive, the power of 
the engine is directly applied to the square 
shaft, avoiding the loss that occurs through 
the friction of the teeth of the gears. 

The revolution of the square shaft is trans¬ 
mitted to the driving wheels, the speed of 
the car therefore corresponding to the speed 
at which the square shaft is driven by the 
gear combinations between it and the coun¬ 
tershaft. To obtain the reverse, which en¬ 
ables the car to be backed without reversing 
the engine, a third gear is introduced be¬ 
tween the low-speed gears of the square shaft 
and countershaft. When two gears are in 
mesh, they revolve in opposite directions, 
but when one of them is in addition meshed 
with a third gear, the first and third will re¬ 
volve in the same direction, and opposite to 
the direction in which the middle gear re¬ 
volves. When the car is going forward, the 


TRANSMISSION 


231 


square shaft and countershaft revolve in op¬ 
posite directions, but when the reverse gear 
is introduced between them, the square shaft 
is revolved in the same direction as the coun¬ 
tershaft, reversing the rotation of the driv¬ 
ing wheels. 

The ends of the teeth of the gears are 
chisel-shaped, instead of being flat, as in or¬ 
dinary gears, so that they will go into mesh 
easily. 

The greatest economy in the operation of a 
gasoline engine results from its running at 
as nearly constant a speed as possible, and 
the gear is therefore changed when the re¬ 
sistance of the road to the movement of the 
car decreases the speed of the engine, or per¬ 
mits it to increase. 

In the progressive change speed gear it is 
necessary to engage and disengage the inter¬ 
mediate gears in passing from low to high, 
or from high to low. The difficulties en¬ 
countered in this operation have caused the 
abandonment of the progressive gear and 


232 MOTOR CAR PRINCIPLES 


the adoption of a construction that makes it 
possible to pass from neutral to any desired 
speed. This construction is known as the 
selective type of sliding change speed gear. 

The selective change speed gear is shown 

* 

in Figure 91, and its control differs from that 
of the progressive type described in that the 
lever has only a short movement forward 
and back, and in addition may slide end¬ 
ways. To the lower end of the lever is at¬ 
tached a shaft that rocks in its bearings as 
the lever is moved forward or back, and 
slides lengthways when the lever is moved 
toward or away from the car. 

The arrangement of the countershaft and 
square shaft is the same as in the progressive 
type, but there are two sets of sliding gears 
instead of one, and these are moved by means 
of arms that extend from rods sliding in 
bearings at the side of the gear case. When 
these rods are slid endways, the gears at¬ 
tached to their arms slide on the square shaft 
to correspond, and go in or out of mesh with 



SECOND SPEED 

Fig. 91.— Selective Type. A, 
sleeve driven by engine; B, 
fixed gear on sleeve; C, fixed 
gear on countershaft; D, low- 
speed gears; E, second-speed 
gears; F, third-speed gears; 

G, clutch for direct drive; H, 
rod and arm for third-speed 
and direct drive; J, rod and 
arm for low and second 
speeds; E, rod and arm for 
reverse; L, rocking shaft finger in groove; M, guide plate and con¬ 
trol lever; N, bevel gears on square shaft and jack shaft; 0, idler 
gear for reverse. 


HIGH SPEED 


233 







































































































































































































































































































































































234 MOTOR CAR PRINCIPLES 


the countershaft gears. Across the ends of 
these rods are grooves, which when the gears 
are in the neutral position are in line with 
the rocking shaft attached to the control 
lever. From the inward end of the rocking 
shaft a finger (L) projects downward into 
the groove; when the grooves are in line, the 
rocking shaft may be slid endways, the finger 
passing from one groove to the next without 
affecting the rods. When the shaft is 
rocked, however, the finger in engaging one 
of the grooves slides the rod endways, shift¬ 
ing the gears controlled by its arm. Moving 
the control lever into such a position that it 
may enter the middle slots of the guide plate 
(M) slides the rocking shaft so that its finger 
projects into the groove of the central slid¬ 
ing rod (J), and if the control lever is then 
pushed forward so that it enters the front 
half of the slot, the sliding rod will be moved 
by the finger in the opposite direction, and 
the low-speed gears (D) will be brought into 
mesh. Bringing the lever back to the cen- 


TRANSMISSION 


235 


tral position will separate the gears, and 
moving it to the back half of the slot will 
slide the same gears in the opposite direc¬ 
tion, meshing the second-speed combination 
(E). Moving the control lever outward so 
that it is in line with the outside slot brings 
the finger into the groove of the sliding rod 
(H) that moves the third and high speeds 
(F and G), the latter being direct drive, and 
the reverse is obtained through the move¬ 
ment of the sliding rod (K) that is engaged 
by the finger when the control lever is in the 
inside slot. The movement of this rod brings 
a third gear (0) into mesh with the low- 
speed gears on the square shaft and counter¬ 
shaft, and the rotation of the countershaft is 
reversed. The arrangement of the control 
lever and its parts is shown in Figure 92. 

While this type is in general use, the gears 
are often so arranged that the direct drive 
combination is reached when the control 
lever is in the third-speed position, the gears 
meshed by the fourth-speed position driving 


236 MOTOR CAR PRINCIPLES 


the square shaft at a still higher speed. This 
high speed can only be used for running un¬ 
der the best road conditions. 



Fig. 92.—Action of Speed Control Lever. 


The advantages of the selective type over 
the progressive are the shorter movements 



















TRANSMISSION 


of the control lever and the ability to pass 
from one speed to any other without the 
necessity of first meshing and unmeshing 
those between, or, in other words, there is a 
neutral position between every combination 
of gears, and from neutral any desired com¬ 
bination may be obtained directly without 
reference to the others. 

In starting up a car fitted with either of 
these types of change-speed mechanism, it 
is necessary to withdraw the clutch before 
sliding the gears, and this is also necessary 
in changing from one combination to an¬ 
other. The square or corresponding shaft of 
a change-speed mechanism is always con¬ 
nected with the driving wheels, and is at rest 
when the car is standing. With the engine 
running, the countershaft will be revolving, 
and it will obviously be difficult to slide the 
stationary gear into mesh with a gear that 
is revolving. When the clutch is withdrawn, 
the countershaft moves only through momen¬ 
tum, and will be brought to a stop by the 


238 MOTOR CAR PRINCIPLES 


contact of the teeth of the sliding gear as 
that is moved against it, the two then easily 
going into mesh. The clutch is then thrown 
in slowly, and will bring the speed of the 
countershaft to the speed of the crank shaft. 

When the car is moving, sliding the gears 
without first withdrawing the clutch will 
bring together two gears that are revolving 
at different speeds, and as it is necessary for 
them to be rotating equally in order that 
they may mesh, either the speed of the car 
must be changed to bring the speed of the 
gear on the square shaft to that of the coun¬ 
tershaft gear, or the speed of the engine must 
be changed to bring the countershaft gear to 
the speed of the gear on the square shaft. If 
the change is from a low to a higher speed, 
the countershaft will be moving much faster 
than the square shaft, and their gears being 
brought into contact will result in the slow¬ 
ing of one and speeding up of the other until 
the speeds are the same, but in so doing the 
ends of the teeth will grind against each 


TRANSMISSION 


239 


other, resulting in the wear of the chisel- 
pointed ends, if not in the breaking of the 
teeth. Withdrawing the clutch obviates this 
difficulty, for it frees the countershaft, per¬ 
mitting its gear to take the speed of the 
square-shaft gear without wear or damage, 
and when the change is made, the slow en¬ 
gagement of the clutch brings the speed of 
both to that required by the crank shaft. 


CHAPTER XIV 
transmission— ( C ontinued) 


W HILE the planetary type of 
change-speed mechanism, which 
is in extensive use for runabouts 
and light commercial wagons, also employs 
gears, their arrangement is along different 
lines. The first three diagrams in Figure 93 
serve to illustrate the principle. 

The gear A in these diagrams is attached 
directly to the crank shaft, and in mesh with 
it are four other gears (B) of the same size. 
Surrounding them is an internal gear (C), 
this being a ring with teeth cut on its inner 
face, the four gears meshing with it. The 
shafts, or studs, on which the four gears re¬ 
volve are supported by a metal ring (D), 
which maintains the gears at equal distances 
from each other. The first diagram shows 
the mechanism in the reverse position, for 

240 



REVERSE 

INTERNAL GEAR C fUTOLFlNG. 
R)M D STATION A AY, SmALL - 
C ears 3 and shaft ce/trt A 
ALL HCrOLY/NG 


SLOYV 6 PE ED 

INTERNAL GEAR C JMr/W/HlK. 
Shaft gear A 


ftl/VC 0 } shall gears 3 A/YO 


All HE not rate 


PRt/YC/PLES OP PLANETARY GEAR TRANS/1/SSlO/Y 


WGH SPEEO 

I NT ERR At GEAR C. RmC O. 
SNAIL CEA/Vd AND SHAFT GEAR 

A Re rot king rr/rn erg me 

SHAFT 


loose SLtere caaay/ng iateanal 

GEA/t AAA LOR SACCO 


e»AAs owo nn_ 

io>t steed 


LOOSE sieere caray/hc jateaeal gcar for Reresse 
AHO small Gears COR LOR JFEEO 


Clutch for 

HIGH STEEP 


CHANS SHAFT STAR, 
TOR ION SATES 


small class for 

low srseo 


QRAHE SALTO FOR AtfCRSE 


5Y>Y>Y>\\Y 



ENGINE CHAN* 
SMALL GEARS FOR RETEROE 


OAir/JYO SPAOCHIT 


SECTION PLANETARY GEAR TflANJ/'l/JJWff 


Fig. 93.—Planetary Type, 

241 























































































































































242 MOTOR CAR PRINCIPLES 


driving the car backward, the car being 
driven by the internal gear. To have the 
internal gear revolve in the direction oppo¬ 
site to that of the crank shaft, as is neces¬ 
sary, the ring supporting the four gears is 
held stationary, with the result that as the 
crank-shaft gear revolves the four gears are 
revolved on their studs. As these gears are 
in mesh with the internal gear, that is re¬ 
volved, and moves in the same direction as 
the four gears and in the opposite direction 
to the crank shaft. 

For the low-speed forward, the ring is re¬ 
leased and the internal gear held stationary, 
the car now being driven by the ring instead 
of by the internal gear. If the four gears 
were free from the internal gear, they and 
their ring would revolve with the crank-shaft 
gear without rotating on their studs, but be¬ 
ing in mesh with the internal gear, they roll 
around it as a wheel rolls along the ground, 
rotating on their studs. A simple experiment 
that will illustrate this motion is to crook 


TRANSMISSION 


243 


the forefinger around a napkin ring or sim¬ 
ilar object, placing a pencil between it and 
the finger, and revolving the ring with the 
other hand. The finger being stationary, the 
pencil, which is revolved in the opposite di¬ 
rection to the ring, will roll along it. In this 
the napkin ring represents the crank-shaft 
gear, the pencil one of the four gears, and 
the finger the internal gear. As the four 
gears roll around, the ring moves also, for 
it is carried by the studs on which the four 
gears revolve. If each of the four gears has 
fifty teeth, and the internal gear two hun¬ 
dred teeth, each gear must make four revolu¬ 
tions in order to roll around the internal gear 
to the point where it started. The crank¬ 
shaft gear also having fifty teeth, it revolves 
at the same speed, and as four revolutions of 
the four gears are necessary in order that 
they may roll completely around the internal 
gear, the crank-shaft gear will make four 
revolutions in the same time. The ring 
moves with the four gears, and revolves 


244 MOTOR CAR PRINCIPLES 


once around the crank shaft in the same time. 
As the car moves according to the rotation 
of this ring, it will go at one quarter the 
speed that it would make if the wheels were 
directly connected with the crank shaft in¬ 
stead of with the ring. 

For the high speed, the internal gear and 
the ring are locked to the crank shaft so that 
all revolve together, the wheels being driven 
by either the ring or the internal gear. 

In these diagrams the drive of the wheels 
is supposed to be shifted from the internal 
gear to the ring, which is not a practical ar¬ 
rangement, and the planetary change-speed 
mechanism as applied to an automobile is 
shown in the lower diagram in Figure 93. 

In this there are two sets of crank-shaft 
gears, gears and rings, and internal gears, 
one set being for the reverse and the other 
for low and high speeds. Between the two 
crank-shaft gears is a loose sleeve, one end 
of which forms the internal gear for the re¬ 
verse, and the other end the ring supporting 


TRANSMISSION 


245 


the studs on which revolve the four gears 
for the low speed. The sprocket for the 
chain drive to the rear axle is carried on this 
sleeve. Two more loose sleeves are on the 
shaft, one forming the ring on which revolve 
the four gears for the reverse, and being ex¬ 
tended to form a brake drum outside of the 
internal gear, and the other carrying the in¬ 
ternal gear for the low-speed combination, its 
outside face serving as a brake drum. 

To obtain the reverse, a brake band is 
tightened on the drum of the reverse com¬ 
bination, which holds stationary the ring 
supporting the four gears, giving the result 
shown on the first diagram of the four gears 
revolving on their studs, and rotating the in¬ 
ternal gear in the direction opposite to that 
of the crank shaft. The sleeve bearing the 
sprocket is thus revolved, and the car backs. 

For the low speed, the reverse brake band 
is loosened, and the internal gear of the low- 
speed combination held stationary by the 
tightening of the brake band surrounding its 


246 MOTOR CAR PRINCIPLES 


drum. The revolution of the crank-shaft 
gear causes the four gears to revolve on their 
studs and to roll around the internal gear, 
revolving the ring and the sleeve bearing the 
sprocket, which now turns in the direction 
opposite to that resulting to the application 
of the reverse, or in the same direction as 
the crank shaft. 

For the high speed, a clutch is engaged 
that locks the internal gear to the crank 
shaft, and the four gears then being held be¬ 
tween these two are carried around with 
them, and the sprocket rotates accordingly. 
When this combination is used, none of the 
gears are in motion, all revolving with the 
crank shaft, but not on their studs. 

The planetary change-speed mechanism 
gives excellent results for light work, but 
having only two speeds forward is not 
adapted to high-powered cars. As the 
speeds result from the tightening of brake 
bands on the drums, there is no danger of 
damaging the gears by mishandling, for the 


TRANSMISSION 


247 


brakes will slip before the teeth will give 
way. The brakes, which are leather-lined 
strips of steel, require attention from the 
wearing of the leather, and the slipping that 
results from oil working in between them and 
their drums. No foot clutch is necessary, 
for the tightening and loosening of the brake 
bands are controlled by a lever; in some de¬ 
signs, the reverse is applied by means of a 
foot pedal, and this may be used in braking 
the car. 


FINAL DRIVE 

From the change-speed mechanism the 
power is passed to the driving wheels by the 

final drive. 

In the most usual construction the engine 
is so placed that the crank shaft is at right 
angles to the axle, and it is therefore neces¬ 
sary to change the direction in which the 
power acts, which is done by means of bevel 
gears. In ordinary spur gears the teeth are 
parallel to the shaft, and the two shafts that 



A 


Fig. 94.—A ; Propeller or Driving-shaft Drive; B, Single-chain 

Drive. 


248 








































































































































































TRANSMISSION 


249 


carry them are parallel, while in bevel gears 
the teeth are at an angle, and the shafts may 
be at right angles to each other. In Figure 
94 the diagram of the single-chain drive 
illustrates a car in which the engine is in the 
center of the frame, and as the crank shaft is 



Fig. 95.—Typical Universal Joint. 


parallel to the axle, the power may be di¬ 
rectly applied. In the illustration of the 
propeller or driving-shaft drive the crank 
shaft is at right angles to the axle, and the 
power is turned by means of the bevel gears 
at the rear axle. 

The single-chain drive can only be used for 
light cars, and is usually applied in connec¬ 
tion with a change-speed mechanism of the 
planetary type. 

The propeller-shaft drive requires the use 





250 MOTOR CAR PRINCIPLES 


of universal joints, which are devices that 
permit one shaft to drive another, even 
though they are at an angle with each other. 
A typical universal joint is illustrated in 
Figure 95. The ends of the shafts bear 
yokes, the ends of which are pivoted to a 
block of metal of + shape. When the two 
shafts are in line, the joint will force one to 
rotate with the other, and this will not be 
prevented if the two are out of line, for then 
the pivots will act, the + swinging on its 
pivots in the yokes. 

The change-speed mechanism is carried on 
the frame of the car, and is therefore sup¬ 
ported by the springs, but the axle end of 
the driving shaft follows the axle as that fol¬ 
lows the inequalities of the road. One end 
of the propeller shaft is therefore compara¬ 
tively stationary, while the other is in con¬ 
stant motion, and if the shaft were inflexible 
it would be jammed in its bearings and 
twisted out of line. This is prevented by the 
universal joints with which the shaft is pro- 



DRIVE! TtiROUGH UNIVERSAL JOINTS 




Fig. 96.—Types of Shaft Drive. 


251 





















































252 MOTOR CAR PRINCIPLES 


vided, there being one and often two in the 
shaft, and usually one between the clutch 
and change-speed mechanism. 

The single-chain and driving-shaft drives 
require the use of a live axle, which is an 
axle that revolves with the wheels. The sim¬ 
ple type of live axle consists of the shaft to 
which the wheels are attached, and the 
housing that contains and supports it (Fig. 
97). This axle is continuous, and usually has 
square ends that fit into the square hubs of 
the wheels so there may be no slipping. The 
second diagram in Figure 98 shows a live 
axle of the floating type, in which the revolv¬ 
ing part serves only to turn the wheels. The 
housing is extended, and the wheels run on 
its ends, the driving part projecting beyond 
the housing and having square ends that are 
secured to the outside of the hubs by square 
caps.' The wheels thus run on the housing, 
which takes the weight of the car from the 
driving part. A live axle must be divided 
into two parts in order that a differential 


O/FreRCNTIAU. 



253 


Fig. 98. Live Axle—Full Floating Type. 




























































































































































































254 MOTOR CAR PRINCIPLES 


gear may be fitted, and the housing must 
therefore be strong enough to support the 
weight and prevent sagging. The efficiency 
of a bevel gear is greatly reduced if the 
teeth are not in their exact mesh, and sag¬ 
ging of the axle will throw them out to such 
an extent that they will be noisy, and wear 
rapidly. The floating type of live axle, in 
relieving the driving part of the weight, has 
a great advantage over the simple type, and 
is in general use. 

With the driving-shaft drive it is neces¬ 
sary to use a torsion rod, which extends from 
the gear case, or a crosspiece of the frame, 
to the rear axle. The necessity for this is 
the tendency of the driving bevel gear to roll 
around on the driven bevel gear rather than 
to revolve it. If it were not for the torsion 
rod, there would be a continual strain on the 
parts because of the tendency of the axle 
housing to revolve around the axle, instead 
of the axle being revolved inside of the hous¬ 
ing. The torsion rod has a flexible joint at 



255 


F IG . 99.— Dead Axle with Driving Shaft. Axle supports bevel gear and differential. The driving shaft 
is supported in bearings at the differential end, and drives the wheels through clutches in the hubs. 
















































































































































256 MOTOR CAR PRINCIPLES 


one end, that permits it to give as the axle 
follows an uneven road surface, but it re¬ 
tains the housing in the correct position, pre¬ 
venting the bevel gears from getting out of 


line. (Fig. 100.) 



In Figure 101 is shown a car with double- 
chain drive, in which the bevel gears that 
change the direction in which the power is 
applied are contained within the gear case 
that incloses the change-speed mechanism. 
As will be seen from Figure 91, the bevel 
gears connect the square shaft with the jack 
shaft, which is a shaft passing across the 






































257 


Fig. 101. —Double Side-chain 








































































































































258 MOTOR CAR PRINCIPLES 


car, and bearing on its ends the sprockets 
by which the wheels are driven. This type 
of drive requires the use of a dead axle, 
which is stationary with the wheels running 
loose on its ends, like the axle and wheels of 
a coach. An axle of this type may have 
great strength with light weight, and is usu¬ 
ally a manganese-bronze or steel forging. 
The sprockets on the rear wheels are bolted 
to the spokes, and should be, of course, ex¬ 
actly in line with the sprockets on the jack 
shaft in order that the chains may run true. 

DIFFERENTIAL 

When a car takes a corner, the outside 
wheels make a larger curve than the inside, 
and cover a longer distance. As the front 
wheels are loose on the axle, they accommo¬ 
date themselves to this; but as both rear 
wheels are driven by the engine, it is neces¬ 
sary to apply a device that will permit them 
to rotate at different speeds without inter¬ 
fering with their driving the car. This is 


TRANSMISSION 


259 


accomplished by means of a compensating’ 
and differential gear. 

To understand the necessity for a differen¬ 
tial, stand behind a wagon, with one hand on 
each tire; push, and if the vehicle is steered 
straight ahead, the hands will move ahead 
equally; but if the vehicle turns, the hand on 
the outside wheel will move ahead faster 
than the other. Now take a stick, and run it 
through the rear wheels so that it bears 
against the spokes; press it forward from its 
center, and if the vehicle moves straight 
ahead, the stick will go forward equally; but 
if the vehicle turns, the outside end of the 
stick will go ahead faster and farther than 
the other, although the pressure is being ap¬ 
plied to its center. 

In applying a simple form of differential 
the axle is divided into two parts, to the 
inner ends of which are fitted bevel gears, 
these being held at a fixed distance apart by 
the construction of the housing (Fig. 102). 
Between the bevel gears and in mesh with 


omv/Mo 

SMAfT- 


SntlL eevFl 6CA0 Ci/WlFO OAf HOtX we 


oniVUTG SHAFT 



SPUR GEAR TYPE 


Fig. 102.—Differentials. 


260 


















































































































































TRANSMISSION 


261 


both of them are small bevel gears, or 
pinions, which may revolve on short studs 
carried on a ring so that they are a fixed dis¬ 
tance apart. When the ring is revolved it 
carries with it the studs and pinions. The 
ring forms a housing that incloses the differ¬ 
ential, and is driven by the single chain or 
driving shaft. To understand the action of 
the differential, imagine the rear wheels of 
a car to be jacked up clear of the ground so 
that they are free to revolve, and the housing 
to be revolved by hand. As it turns, the 
driving wheels will turn also, for the resist¬ 
ance to each is the same, and the pinions, 
being in mesh with both bevel gears, cannot 
revolve on their studs. If one of the wheels 
is now held stationary and the housing re¬ 
volved, the bevel pinions will revolve on their 
studs, and roll around on the stationary gear; 
this will drive the gear of the free wheel at 
twice the speed of the housing. The revolv¬ 
ing of the housing in the first instance caused 
the wheels to turn equally at the speed of 


262 MOTOR CAR PRINCIPLES 


the ring, and in the second permitted one 
to remain stationary while the other turned 
at twice the speed of the housing, the speed 
of the latter being unchanged. The first is 
the effect when the car moves straight ahead, 
and the second the result if the car could 
make so short a turn that it would pivot on 
one wheel. 

With the wheels jacked up, hold one hand 
lightly against one of the wheels, so that, 
while it may turn, there is more resistance 
to it than to the other. If the housing is now 
revolved, the bevel pinions will revolve on 
their studs, and roll slowly around the gear 
of the wheel that presents the resistance, the 
free wheel being revolved at a higher speed 
than the housing. This is the condition when 
the car takes a corner, for there is then more 
resistance to the inside than to the outside 
wheel, and it slows down; this will start the 
pinions revolving on their studs, and they 
will drive the outside wheel correspondingly 
faster. 


TRANSMISSION 


263 


With the housing revolving at a fixed 
speed, the outside wheel will revolve as much 
faster as the inner wheel is revolving slower; 
for an illustration, if the housing makes fifty 
revolutions a minute, and the inner wheel is 
slowed to forty, the outer will be driven at 
sixty revolutions. 

If one wheel of a jacked-up car is revolved 
by hand, the other wheel will revolve in the 
opposite direction. This is caused by the 
housing remaining stationary and the pin¬ 
ions being revolved on their studs by the 
turning of the wheel, the movement being 
transmitted to the free bevel gear and wheel 
in the reverse direction. 

The bevel gear differential described was 
the early type, but a more recent design em¬ 
ploys spur gears. The axle ends carry spur 
instead of bevel gears, these being in mesh 
with other spur gears that are long, but of 
small diameter. These small gears are in 
pairs, as shown in Figure 102, being in mesh 
with each other at their inner ends, and each 


264 MOTOR CAR PRINCIPLES 


member of a pair meshing with one of the 
axle gears. The small gears revolve on studs 
supported by the housing that is revolved by 
the drive, the studs in this case being paral¬ 
lel with the axle instead of at right angles 
to it, as are the studs in the bevel-gear type. 

If the small gears meshed only with the 
axle gears, and not with each other, revolv¬ 
ing the housing would cause them to roll 
around the axle gears, all rotating on their 
studs in the same direction, and the axle 
gears remaining stationary. Being in mesh 
with each other, they cannot revolve in the 
same direction, for when two gears are in 
mesh they must revolve in opposite direc¬ 
tions. Thus the small gears cannot roll 
around on the axle gears when the housing is 
revolved, and if there is equal resistance to 
the turning of the wheels, the small gears 
will not revolve on tlieir studs, but will carry 
the axle gears with them. 

If the car is turning a corner, the greater 
resistance to the inner wheel will cause the 


TRANSMISSION 


265 


small gears to revolve on their studs, rolling 
around the resisting gear and driving the 
other correspondingly faster. 

On cars with double-chain drive, the dif¬ 
ferential is fitted to the jack shaft, and 
of course receives the drive from the 
change-speed mechanism through its hous¬ 
ing. 

Both the driving-shaft and double-chain 
drive have points of advantage and of weak¬ 
ness, and each type has its advocates. For 
the double chain, great strength can be 
claimed with light weight, as the axle is in 
one piece, and perfectly adapted to support 
the car. Against it is the difficulty of keep¬ 
ing the chains properly lubricated, and their 
consequent wear and stretching. The driv¬ 
ing-shaft type has the advantage of the per¬ 
fect lubrication of the parts, for all may be 
inclosed and running in oil or grease; the 
rear axle must be divided, however, which 
requires it to be heavily braced in order that 
the weight imposed on it may not bend or 


266 MOTOR CAR PRINCIPLES 


spring it out of line. Where a bent dead axle 
can be straightened by a blacksmith, a sim¬ 
ilar condition in a live axle requires the serv¬ 
ices of an expert mechanic; on the other 
hand, bevel gears make less noise than 
chains. 


DRIVING-GEAR RATIOS 

Even when on the direct drive, the crank 
shaft makes more revolutions than the rear 
wheels, in order that the momentum of the 
moving parts of the engine may be sufficient 
to keep the car in motion. On shaft-driven 
cars, the bevel on the driving shaft has fewer 
teeth than that on the axle, so that it re¬ 
volves more than once to one revolution of 
the axle. On chain-driven cars, the driving 
sprockets are smaller than those driven. 
This driving-gear ratio, as it is called, varies 
from one and a half to three and a half, or, 
in other words, the wheels revolve once while 
the driving shaft or sprocket makes from one 


TRANSMISSION 


267 


and a half to three and a half revolutions. 
Other conditions remaining equal, a higher 
driving gear gives the car lower speed, but 
greater ability in hill-climbing and the tra¬ 
versing of heavy roads. 


CHAPTER XV 


RUNNING GEAR 


T HE steering of a motor car, or the 
change in the direction of its move¬ 
ment, is effected by changing the 
position of its steering wheels, usually those 
in front, in relation to the rear wheels. In 
a horse-drawn vehicle, the axles are parallel 
when it is moving straight, as are also the 
planes of its front and rear wheels. To turn 
the vehicle to one side or the other the front * 
axle is swung so that it is out of parallel 
with the rear axles, the vehicle turning to 
the side on which the axles would meet if 
they were extended. This construction re¬ 
quires the wheels to run loose on the axle, 
and the axle to be permitted to swing on the 
pivot by which it is attached to the body of 
the vehicle. 

Such a construction would be imprac- 

268 


RUNNING GEAR 


269 


ticable for an automobile, because the weight 
resting on the front axle would require the 







/ \ 











Fig. 103.—Drag Link Positions. 




pivot to be of greater strength and stiffness 
than could be conveniently obtained, and be- 












































































270 MOTOR CAR PRINCIPLES 


cause of the effort that would be necessary 
to swing the axle in steering. The front axle 
of an automobile is stationary, and the steer¬ 
ing effect is obtained by pivoting short 
pieces to its ends, these carrying the wheels. 
From these pivoted ends, called knuckles, 
extend short steering arms, which are con¬ 
nected by a drag link, so that moving the 
drag link moves the pivoted ends of the axle 
and the wheels to correspond (Fig. 103). 

For a wheel to follow a curved path with¬ 
out slipping, it must be at all times tangent 
to the path, and will be perpendicular to a 
radius of the curve at that point. The front 
axle of a horse-drawn vehicle points toward 
the center of the circle on which the vehicle 
may be turning and forms part of the radius, 
the wheels, of course, being perpendicular to 
it (Fig. 104, C). As the main part of the 
front axle of an automobile is stationary, 
only its pivoted ends may point to the center 
of the circle, and this must occur in order 
that the wheels may be tangent to the curve 



\ 

l 

I 

I 

I 

I 


I 

I 

I 


271 





















272 MOTOR CAR PRINCIPLES 


(Fig. 104, A). Both axle ends point to the 
center, but along different radii; if both 
pointed along the same radius, it would 
necessitate their being in line with the sta¬ 
tionary part of the axle, which then also 
would be part of the radius. As the axle 
ends are in line with different radii of the 
same curve, it follows that the wheels are 
perpendicular to different radii, and not 
parallel with each other, a condition impos¬ 
sible in horse-drawn vehicles. The front 
wheels of an automobile are parallel with 
each other when the axle ends are in line 
with the stationary part, but go out of paral¬ 
lel as soon as they are at an angle with it, 
as is the case when the car takes a curve. 

If the steering arms project from the 
knuckles at right angles to the axle ends on 
which the wheels revolve, moving the drag 
link would move each knuckle through an 
equal angle, and the wheels would be paral¬ 
lel at all times (Fig. 104, B). This is pre¬ 
vented by so constructing the knuckles that 


RUNNING GEAR 


273 


the steering arms incline toward each other, 
with the result that, when the drag link is 
moved, one of the wheels swings through a 
greater angle than the other, the difference 
between the angle of each steering arm and 
the stationary part of the axle increasing 
with a greater movement of the drag link. 

The control of the drag link is obtained 
either by a steering lever or wheel. When 
the steering lever is moved by the driver, the 
drag link is moved to correspond by a con¬ 
necting rod, and this type is usual in small 
cars. It is impracticable for heavy cars be¬ 
cause it is reversible; that is, the moving of 
the steering wheels moves the lever, and a 
firm grasp is required to prevent the shock 
of striking a stone or rut from tearing the 
lever from the hand and changing the course 
of the car. The irreversible type is used for 
all but the lightest cars, and while it permits 
the driver to change the direction of the 
front wheels it prevents any movement from 
being transmitted from the wheels to the 


274 MOTOR CAR PRINCIPLES 


steering wheel or lever. The serew-and-nut 
type of irreversible steering mechanism 
(Fig. 105, B) consists of a heavy screw at- 



Fig. IOo. Steering Mechanisms. A, worm and worm 
wheel steering gear; B, nut and screw steering gear. 


tached to the lower end of the shaft that re¬ 
volves when the driver turns the steering: 
wheel. The screw passes through a nut that 
is held in guides so that it cannot revolve, 
and is therefore moved up or down when the 
screw is turned by the steering wheel. From 
the nut extends an arm that is connected to 



































RUNNING GEAR 


275 


the drag link, so that its movement is trans¬ 
mitted to the wheels. The turning of the 
steering wheel thus moves the nut and the 
front wheels, hut a movement of the front 
wheels from any other cause is prevented, 
because no pressure on the nut can revolve 
the screw. Another type is the worm-and- 
worm wheel, or worm-and-segment (Fig. 105, 
(A), which, while of different construction, 
depends on the same principle that the move¬ 
ment of the worm or screw can move a worm 
wheel or nut in mesh with it, but the move¬ 
ment cannot be reversed. 

The stationary part of the front axle of 
an automobile is usually a forging, and must 
be of considerable strength in order to sup¬ 
port the weight imposed upon it by the en¬ 
gine. It is usually bent down in the center, 
in order that it may be the lowest point of 
the mechanism, thus to receive possible 
blows of stones or other high points of the 
road that would cause serious damage should 
they strike the crank case or fly wheel. 


276 MOTOR CAR PRINCIPLES 


BRAKES 

The brakes used in controlling the speed 
of an automobile may be as many as four in 
number, and there should be at least two, for 
on them depends the safety of the car. 
Brakes are of two types, expanding and con¬ 
tracting, and usually operate through the 
friction between a drum and a band that sur¬ 
rounds it, or blocks that press against its in¬ 
ner surface. The band or contracting brake 
may be either single- or double-acting, the 
latter being by far the better. In a single- 
acting band brake (Fig. 106) a flexible steel 
band surrounds the drum, one end being 
made fast to the frame of the car or some 
other stationary part, and pressure applied 
by drawing the free end. The friction 
caused by the binding of the leather or fiber 
lining of the band on the drum restrains the 
movement if the drum is revolving in the 
opposite direction to the pull, but there is 
little effect if the revolution is in the same 


RUNNING GEAR 


277 


direction as the pull. In the double-acting 
type, both ends of the band are pulled, and 
the drum is prevented from revolving in 



Single acting band bbanl 


DOUBLE ACTING BAND 3ft Ah E 



Fig. 106. —Three Varieties 
of Brakes. 

either direction. The 
single-acting type will 
be satisfactory when the 
car moves forward, but 


running downhill backward, while the double¬ 


acting brake holds it in either direction. The 
expanding brake usually consists of two 
bronze shoes, of such shape that they fit the 









278 MOTOR CAR PRINCIPLES 

interior surface of the drum. The shoes are 
pivoted together at one end, and so arranged 
that the pull of the brake pedal or lever ex¬ 
pands them, binding them against the drum 
(Fig. 106). When pressure is not being ex¬ 
erted, a coil spring, not shown in the diagram, 
holds them together and out of contact with 
the drum. 

Brake drums are usually attached to the 
spokes of the rear wheels, and one drum 
often serves for both an expanding and a 
contracting brake. Brake drums are also 
applied to the jack shaft, or to an extension 
of the countershaft of the change-speed 
mechanism. It is usual to have one set of 
brakes controlled by a foot pedal, and an¬ 
other, called the emergency brake, by a lever 
at the side of the car. The foot brake, or 
running brake, is sometimes connected to the 
clutch, so that applying it throws out the 
clutch. The emergency brake is also con¬ 
nected in the same manner in some makes 
of automobiles, but this is not recommended, 


RUNNING GEAR 


279 


for if it is necessary to stop the car when 
going uphill, the brakes must be released be¬ 
fore the clutch can be thrown in, and the 
possibility of the car starting downhill back¬ 
ward before power can be applied, the chance 
of stalling the engine through this, and the 
danger of the combination to any but an ex¬ 
perienced driver, make it advisable to have 
the emergency brake separate from any con¬ 
nection with the clutch. 

Band brakes are usually lined with 
leather, to increase the friction between the 
band and the drum, and this often gives rise 
to troubles in the burning of the leather 
when the brake is applied for a considerable 
period, as in the descent of a long hill. The 
emergency brake has advantages in that it 
operates through the friction of metal 
against metal, but excessive heat from con¬ 
tinued application may be enough to melt the 
metal and fuse together the shoe and drum. 
For long descents, it is well to use the motor 
as a brake, for it is logical to consider that 


280 MOTOR CAR PRINCIPLES 


the means of propulsion may also be the 
means of retarding, as the wind that urges a 
sailboat forward may also bring it to a stop. 
It is obviously impossible to reverse the 
motor or gears, but by switching off the igni¬ 
tion circuit and throttling down, the forward 
movement of the car is caused to operate the 
motor, and the work necessary in driving the 
motor as an air compressor is sufficient to 
check the speed. The effect is so great that 
if the low-speed gears are engaged, the car 
will be brought to a stop even on a steep 
hill. Another advantage of this course is 
that it gives the motor an opportunity to 
cool, which is often necessary after a long 
ascent. 

In case of the failure of the brakes to oper¬ 
ate, which may result from poor adjustment 
or worn bands and shoes, the speed may be 
checked by throwing out the clutch, switch¬ 
ing off the ignition, engaging the inter¬ 
mediate speed gears, and letting in the clutch 
very slowly. Great care must be taken that 


RUNNING GEAR 


281 


the clutch is not permitted to bind sud¬ 
denly, for that would probably result in the 
stripping of the gears. If the low-speed 
gears are engaged, the checking would be so 
sudden, no matter how slowly the clutch 
might be engaged, that the shock would 
probably throw the passengers from their 
seats. 

The failure of the brakes when descending 
a hill produces a condition that requires skill 
and coolness, and danger can only be averted 
by a steady hand and a clear head. 

Brakes applied to the rear wheels must 
have an equal grip on each, for if one binds 
more tightly than the other, the car will 
have a tendency to skid, or slide sideways. 
In the best cars this is taken care of by an 
equalizer, in which the pull of the lever or 
pedal is not applied directly to the brakes, 
but to the center of a bar, each end of which 
is connected to one of the bands or shoes. 
The lever action of this bar distributes the 
pull equally between the two brakes, and un- 


282 MOTOR CAR PRINCIPLES 


less there is a great difference in the grip on 
the two drums, as might be the case if one 
were oily and the other dry, the effect will 
be the same on both sides. 

TIRES 

For low speeds, solid tires give good re¬ 
sults in traction and the absorption of jolts 
from small obstacles, but for anything above 
six or eight miles an hour, pneumatic tires 
are a necessity in preventing the rapid shak¬ 
ing to pieces of the mechanism. A hard tire 
touches the ground at but one point, and its 
grip on the road will be much less than that 
of a pneumatic tire which, being slightly 
flattened by the weight it bears, presents an 
oval or elliptical surface to the road. While 
a pebble will force a solid tire to roll over it, 
it will sink into a pneumatic tire, and the 
jolt that it might cause will be entirely ab¬ 
sorbed. Pneumatic tires are formed of al¬ 
ternate layers of heavy canvaslike fabric 
and soft rubber, and the processes through 


RUNNING GEAR 


283 


which they are put in manufacture are sup¬ 
posed to effect their perfect combination; but 
as it is not the nature of rubber to be ab¬ 
sorbed by the fabric, the layers are only 
bound together by its tenacity. The bend¬ 
ing of the sides of the tire under the weight 
of the car tends to separate these layers, and 
water or dirt entering between them through 
cuts quickly brings ruin; it is obvious that 
the less the sides bend, the smaller will be 
the opportunity for the layers to work apart. 
A pneumatic tire should always be pumped 
as hard as possible, so that it stands up prac¬ 
tically round under a loaded car. While the 
car will ride a little harder under these con¬ 
ditions than when the tires are soft, there 
will be greater resistance to punctures, and 
the life of the tires will be increased. The 
normal wear to a tire should give it a smooth 
surface, but if it is noticed that the tread is 
rough and uneven, it may be taken for 
granted that the wheels do not run true. 
Rear wheels will be thrown out of true by the 


284 MOTOR CAR PRINCIPLES 


springing or bending of the axle, and front 
wheels also from this cause, but more prob¬ 
ably from faulty adjustment of the steering 
mechanism or the bending of the drag link 
or steering arms. 

The grip of the tire on the road is much 
affected by the nature of the surface, the 
traction on dry macadam being much 
greater than on wet asphalt. When the pull 
of the engine on the wheel exceeds the grip 
of the tire on the road, there will be a slip, 
and the wheel will revolve without moving 
the car. This will wear the tread of the tire 
far more rapidly than will ordinary running. 
The better the traction of the tires on the 
road surface, the less will be the tendency 
of the car to skid or slide sideways, and less 
power will be lost through the slipping of 
the wheels. To reduce the chance of slip¬ 
ping, because of wet asphalt or muddy roads, 
various devices are in use, all of which en¬ 
circle the tread of the tire, and present a 
rough surface. The form in most general 


RUNNING GEAR 285 

use consists of chains that fit across the 
tread, these being detachable and used only 
in case of necessity. While it is often done, 
it is nevertheless bad practice to apply 
chains or other anti-skid devices to only one 
of the rear wheels instead of to both, for it 
increases the diameter of the wheel and 
makes a difference in the resistance against 
the wheel, causing the differential to operate 
at all times. The differential is not con¬ 
structed to operate steadily, and will wear 
rapidly if forced to do so. 

SPRINGS 

In addition to tires, an automobile is fitted 
with springs, which are necessary to absorb 
the shocks and jolts that are too great to be 
taken up by the tires. These are usually full 
or half elliptic (Fig. 107), and made of flat 
plates, or leaves, of different lengths, the 
small being placed on the large, and all 
bound together at the center. The combined 
action of the springs and tires permits the 


286 MOTOR CAR PRINCIPLES 


frame and body of the car to move in a 
nearly straight line, while the wheels and 
axles follow the inequalities of the road. 
When springs break, as is frequently the 
case, it is from the rebound of the body that 



Fig. 107.—A, Full Elliptic Spring; B, Half Elliptic 


Spring. 

results when the wheels drop into a deep 
hole, the upward movement separating the 
leaves, and the entire strain coming on the 
long leaves alone. To prevent this, shock 
absorbers are recommended, which permit 
the springs to have a certain amount of ac¬ 
tion, but check them if they tend to expand 
or compress to too great an extent. They 
act either by the friction between metal 
plates and washers, or by air or oil in a cylin¬ 
der that permits a piston to move freely to a 














RUNNING GEAR 


287 


certain degree, but presents resistance to a 
greater motion. Shock absorbers are placed 
between the axles and frame, and there 
should be four, two to each axle. 

DISTANCE RODS 

As the springs are placed between the 
axles and body and are flexible, it is neces¬ 
sary to provide some method of preventing 
an obstruction in the road from twisting the 
axle, as might result if one wheel struck 
heavy sand or a stone while its mate was on 
good surface. A twist of this sort would 
throw the axle out of line with the drive and 
bind the chain or driving shaft. 

To prevent this, radius or distance rods are 
attached to the axle, one on each side, ex¬ 
tending to a point well forward on the frame 
(Fig. 108). These rods are pivoted to the 
frame, and have a loose joint on the axle, so 
that the latter is free to move up and down, 
but prevented from moving forward or back. 
Distance rods are adjustable, and on chain- 


288 MOTOR CAR PRINCIPLES 


driven ears serve to adjust the chains, which 
are tightened by lengthening the rods and 
slackened by shortening them. 




spfunc 


DHTfiHCE BOO 


JACK JHAP7 


DlFF T//U 



CHAHCf SPf/0 
GEAR 




SMOCK F 7 


DJSTAKCE fiQD 


cnJ 


6 PR INC 



AXLE 


PAR ME 


Fig. 108 .—Distance or Radius Rods. 















































CHAPTER XVI 


MAINTENANCE AND CONSTRUCTION 

I N order that an automobile may be main¬ 
tained at its highest efficiency, a con¬ 
stant watch must be kept over all of 
its parts, and repairs and replacements made 
as soon as the necessity is apparent. A worn 
bearing or loose part may continue to oper¬ 
ate, but the wear will be far greater than 
would occur under normal conditions, and 
may result in serious breakage. A system of 
inspection to be gone through every time 
that the car is used will keep the driver in¬ 
formed as to its condition, and it is best to 
form the habit of doing this at the end of a 
run rather than before, for then the necessity 
for making readjustments or repairs will be 
fresh on the mind. 


289 


290 MOTOR CAR PRINCIPLES 


INSPECTION 

The condition of the ignition circuit and 
of the compression will be shown in revolv¬ 
ing the crank shaft twice, and the action of 
the carburetor may be ascertained at the 
same time. Pushing the car across the floor 
will show the presence of tight brakes or 
wheel bearings, and the tires may then be ex¬ 
amined for cuts. Beginning at the front of 
the car, every bearing not fed by the lubri¬ 
cator should be oiled, and all grease cups 
given a slight turn, those that are empty or 
nearly so being filled. While this is being 
done, a watch may be kept for nuts and bolts 
that may have been loosened by the vibra¬ 
tions. 

WASHING 

The car should be washed with clear, cold 
water only, and mud floated off; to remove 
mud by rubbing or any other method than 
sluicing it away by the action of a gentle 
stream of water will scratch the varnish and 


MAINTENANCE, CONSTRUCTION 291 


ruin the appearance of the car. When clean, 
the varnished parts may be dried with 
chamois or wash leather, and the finish re¬ 
tained by a light coating of a good furniture 
polish, which is to be immediately dried by 
rubbing. 

The tires may be cleaned by sponging, but 
water should not be allowed to settle in the 
head. On cars having the gravity system of 
gasoline feed, the water should not be per¬ 
mitted to splash on the tank, for it will enter 
through the vent. Water should also be 
kept from the upholstery, for if it enters the 
folds and buttonholes it will cause rotting. 

THE TIRES 

Light and heat are the worst enemies of 
rubber; spare tires should be kept in a cool, 
dark place, and protected from dust and 
moisture. French chalk, or some similar 
preparation, should be well dusted over the 
shoes and tubes, and if the tubes are folded, 
they should occasionally be opened and re- 


292 MOTOR CAR PRINCIPLES 


folded in fresh places, to prevent the forma¬ 
tion of creases. The spare tire that is car¬ 
ried on the car should be kept in a casing, 
and because a dark surface will absorb more 
heat than a light, the casing should be tan, 
gray, or white rather than black. The casing 
should be as proof as possible against mois¬ 
ture, but for safety should occasionally be 
removed and aired. The position of the shoe 
in the holders should be changed every little 
while, in order that the straps may not cut 
into the bead. 

The tires on the wheels should frequently 
be examined, and any cuts filled with strong 
cement, for otherwise water and sand will 
work in to form blisters and to separate the 
layers of fabric from the rubber. The cut¬ 
ting of tires can be reduced by withdrawing 
the clutch when crossing broken stones, the 
car coasting over them; driving the car over 
such a surface will force the tires against the 
sharp edges, and cutting will result more 
surely than when the tire rolls over them. 


MAINTENANCE, CONSTRUCTION 293 


CARE OF THE ENGINE 

The carbon deposits that will form in the 
combustion space will in time tend to stick 
the piston rings in their grooves, and this 
may be prevented by squirting a few drops 
of kerosene oil into the cylinders and crank¬ 
ing the engine to distribute it. This should 
be done at the end of a run, and the engine 
permitted to stand in that condition. The 
first explosions will vaporize the kerosene 
and drive it off unless too much has been 
used, when there will be a tendency to foul 
the spark plugs. 

The lubricating oil should be drained out 
of the crank case every five hundred miles, 
and the case washed out with kerosene be¬ 
fore refilling it with fresh oil. Gasoline has 
too great a cutting action to warrant its use 
for this, as it cleans down to the bare metal, 
while kerosene removes the dirt and grease, 
leaving a good surface. The case should be 
filled with oil to such a depth that the con- 


294 MOTOR CAR PRINCIPLES 

necting rods will dip into it from a half inch 
to an inch. 

The same should be done with the change- 
speed gear case every thousand to fifteen 
hundred miles, for the particles of metal that 
will be ground from the gears will injure the 
teeth and bearings. In refilling, the smallest 
gear should project about an inch into the 
oil. If the differential is packed in grease, 
it will run for an entire season with one fill¬ 
ing, but if it runs in oil it should be cleaned 
and washed two or three times a year. The 
bevel gear case of a shaft-driven car should 
receive the same attention. 

CARE OF CHAINS 

Properly lubricated chains should run for 
at least a thousand miles without attention. 
Because of their exposed position they 
should be protected against undue wear, and 
this is best attained by soaking them, when 
thoroughly cleaned, in melted tallow, work¬ 
ing each joint in order that the liquid may 


MAINTENANCE, CONSTRUCTION 295 

penetrate. The chain should be hung up to 
cool and dry, the surplus tallow being wiped 
off. The hardened tallow in the joints will 
prevent grit from working in, and is a lubri¬ 
cant as well. To clean a chain, soak it in 
kerosene, working each joint to remove the 
grit. The stretching of the chain may be 
taken up by lengthening the radius rods, but 
when the stretching reaches a point that per¬ 
mits it, the chain should be shortened by the 
removal of a link, and the rods readjusted. 
If a complete chain is not carried as a spare 
part, the kit should always include a few 
extra links for emergency repairs. These 
are not difficult to apply, being secured in 
position by nuts instead of by burring over 
the ends of the rivets. 

VALVE GRINDING 

To grind a pitted or worn mechanically 
operated valve, the pressure should be re¬ 
leased by compressing the spring and re¬ 
moving the key or other device by which it 


296 MOTOR CAR PRINCIPLES 


is held in place. On removing the plug over 
the valve pocket, the upper surface of the 
valve disk will he exposed, and it will be 
found to be provided with a slot. While 
many grinding pastes may be purchased, 
good results will be obtained by mixing ma¬ 
chine oil with flour of emery until it is thick. 
Plugging the opening from the valve pocket 
to the combustion space with cotton waste to 
prevent the paste from entering the cylinder, 
spread it on the valve disk and seat, and ro¬ 
tate the disk on its seat with a screwdriver, 
preferably by means of a bit brace. Every 
little while the disk should be lifted and re¬ 
placed on the seat in a new position, in order 
to distribute the wear evenly, and the grind¬ 
ing continued until a smooth surface shows 
all around both disk and seat. It is not nec¬ 
essary to smooth the entire surface of the 
disk and seat, for the pressure will be re¬ 
tained by a narrower surface. 

An automatic valve may be removed from 
the cylinder by unscrewing or unbolting its 


MAINTENANCE, CONSTRUCTION 297 


cage, and after releasing the spring the cage 
may be held in a vise while the grinding is 
performed. 

After grinding, all traces of the paste 
should be removed by washing with gasoline, 
for any particles that remain will cause rapid 
wear. When replacing the spring, that of 
the mechanically operated valve will be 
found difficult to compress to the point at 
which the key or washer may be slipped into 
position, and to simplify this many engines 
are built with a knob or boss on the cylinder 
to serve as a fulcrum by which a forked lever 
may be used. If this is not the case, the 
spring may be sufficiently compressed in a 
vise, and bound endwise with wire to retain 
it, the wire being cut when the spring and 
key are in position. 

CARE OF STEERING MECHANISM 

A failure of the steering mechanism will 
cause a wreck more surely and quickly than 
the break-down of any other part of the car, 


298 MOTOR CAR PRINCIPLES 

and the best protection is absolute knowledge 
that it is in perfect condition. All joints 
should he kept well lubricated, and protected 
from dust; the leather protectors that are 
furnished do not accomplish this any too 
well, but they are much better than nothing, 
and if the joints are packed with grease be¬ 
fore applying them, the results will be good. 
While guarding against stiffness, there 
should be very little play or lost motion in 
the mechanism, and the parts should be fre¬ 
quently examined for bent rods and loose 
joints. A bend in the drag link or steering 
knuckles will throw the front wheels out of 
true, in which case the tires will be badly 
worn. When going straight ahead, the 
wheels should be parallel; if this is the case, 
the angles of the steering arms will give the 
proper track when making a turn. 

CARE OF SPRINGS 

The springs of an automobile are in con¬ 
stant motion, and should be as carefully 


MAINTENANCE, CONSTRUCTION 299 


lubricated as the other parts of a car. The 
spring hangers by which the two halves of a 
full elliptic spring are joined, or by which a 
half elliptic spring is attached to the frame, 
are often provided with grease cups, but in 
the absence of these the parts should be fre¬ 
quently oiled. Once a season fresh lubricant 
should be applied to them. The leaves of a 
spring may usually be separated enough for 
this by jacking up the body, applying the 
jack to the frame; the springs will thus be 
relieved of the weight, and the leaves will 
separate sufficiently to permit heavy grease 
or graphite to be introduced between them 
by means of a table knife. If the springs 
are too heavy to permit this, they must be 
taken apart, which may be done by removing 
them from the car and releasing the clips 
by which they are held together. In reassem¬ 
bling a spring, it may be clamped in a vise, 
when the clip may easily be secured. 


300 MOTOR CAR PRINCIPLES 


ADJUSTING VIBRATORS 

In adjusting the vibrators, the best guide 
is the running of the engine. The musical 
tone that they make is misleading, for a dif¬ 
ference in the steel of which the blades are 
made, or in the quality of the core, will pro¬ 
duce a difference in the tone, and because 
two vibrators sound alike is not proof that 
they are producing equal secondary sparks. 
With a one-cylinder engine, the adjusting 
screw may be turned until the engine is run¬ 
ning at its best, while at the same time there 
is the smallest spark between the vibrator 
contacts. The adjustment of the vibrators 
of a multicylinder engine is proceeded with 
along similar lines, all of the blades but one 
being held down, while the free blade is ad¬ 
justed until the best results are obtained in 
the operation of the cylinder to which it cor¬ 
responds, and the smallness of the spark be¬ 
tween the vibrator contacts. When one is 
correct, it is held down and another released, 


MAINTENANCE, CONSTRUCTION SOI 


this process being continued until all are 
adjusted. 

ADJUSTING THE CARBURETOR 

When adjusting a carburetor, it must be 
remembered that the proportion of liquid 
gasoline to air in a correct mixture is very 
small; because this is not well understood, a 
rich mixture is present far more commonly 
than a poor one. To begin at the beginning, 
close both the gasoline and auxiliary air in¬ 
lets, and, opening the gasoline adjustment a 
very little at a time, crank the engine un¬ 
til combustion is secured, the spark being 
retarded and the throttle nearly closed. 
When the engine runs, open the relief 
cocks and note the color of the flame that 
shoots out. A poor mixture will produce 
a yellow flame, and a rich mixture a red 
and smoky flame, with black smoke at 
the exhaust and a smell of gasoline. The 
flame of a correct mixture is blue and hardly 
visible. On securing a correct mixture at 


302 MOTOR CAR PRINCIPLES 


low speed, advance the spark and open the 
throttle to speed np the engine, and the mix¬ 
ture will at once become too rich. Adjusting 
the auxiliary air inlet by weakening the ten¬ 
sion of its spring will bring the mixture to 
approximately correct proportions. A more 
careful adjustment under road conditions 
can be obtained by adjusting the air inlet 
while the car is being operated, for the posi¬ 
tion of the carburetor is usually such that 
this may be done while standing or kneeling 
on the running board. 

Faulty adjustment of the carburetor is 
often suspected when the real source is in the 
throttle or governor connections. The bend¬ 
ing of a rod connecting the throttle with 
either the foot, hand, or governor control, or 
the wear of the joints, will throw the car¬ 
buretor out, and the possible failure of these 
parts must be borne in mind accordingly. 


MAINTENANCE, CONSTRUCTION 303 


SETTING THE VALVES 

In setting or timing the valves of a gaso¬ 
line engine, the point to be considered is the 
closing of the exhaust valve, for upon this 
good results depend. If this valve is held 
open too long, the burned bases driven out 
will be drawn back into the cylinder, and if 
it closes too soon the greatest possible quan¬ 
tity of burned gases will not have been ex¬ 
pelled. The many experiments carried on by 
the manufacturers, and the attention that 
they must pay to this point, result in the de¬ 
livery of cars with valves correctly timed, 
and usually with marks made on the two-to- 
one gears to guide in resetting them. In the 
absence of these guides, the setting of valves 
need not be difficult, although experimenting 
is required to secure the best results. The 
first step is to locate the position of the pis¬ 
ton in the cylinder. There is always an 

V 

opening in the cylinder head—a relief cock, 
the spark-plug opening, or other—and a stiff 


304 MOTOR CAR PRINCIPLES 


wire may be dropped through it, with its 
lower end resting on the piston and its upper 
end projecting. As the piston is moved by 
cranking the engine, the wire will move with 
it, and is to be marked with a file at its high¬ 
est and lowest positions. While no fixed rule 
can be laid down, it may be said that in gen¬ 
eral the exhaust valve should close when the 
piston has made from eV to 3 V inch of its 
outward stroke. The two-to-one gears hav¬ 
ing been unmeshed, the cam shaft may be re¬ 
volved in its bearings by hand; cranking 
slowly, move the piston down from its high¬ 
est point to that at which the exhaust should 
close, and hold it there. Revolve the cam 
shaft until the nose of the cam is passing 
from under the roller of the valve-lifter rod, 
and the valve just closed. This point may be 
accurately ascertained by placing a strip of 
thin paper between the valve-lifter rod and 
valve stem; when the cam is acting on the 
valve-lifter rod, the paper will be pinched, 
but the seating of the valve will release it. 


MAINTENANCE, CONSTRUCTION 305 


When the paper can be pulled out, mesh the 
two-to-one gears, and the relations thus 
established between the crank and the cam 
shafts will be maintained. Cranking the en¬ 
gine a few times, using the strip of paper, 
will verify results, and the engine may then 
be started and the effect noted. If the run¬ 
ning is not satisfactory, unmesh the gears, 
and mesh them with a difference of one tooth, 
first one way and then the other, noting re¬ 
sults, and retaining the most satisfactory 
position. 

Cams are often cut in one piece with the 
cam shaft, and the gear keyed on the 
end; there is therefore no chance to make 
a finer adjustment than what is permitted by 
shifting the gears one tooth at a time. On 
multicylinder engines, one cam shaft oper¬ 
ates all of the exhaust valves, and the setting 
of one valve sets all. 

When inlet valves are of the mechanically 
operated type, but controlled by a separate 
cam shaft, this must be set in a similar man- 


306 MOTOR CAR PRINCIPLES 


ner. The nose of the cam should just be com¬ 
ing into contact with the push rod roller at 
the instant when the exhaust valve is com¬ 
pletely closed. This should occur as the pis¬ 
ton begins to move outward on the inlet 
stroke, the exact position being determined 
by experiment. 

When the cams are so badly worn that if 
they are set to open correctly they close too 
soon, the best remedy is a set of new cams; 
for while the brazing of a strip of brass to 
the sides of the cams can be resorted to, the 
result is only temporary at best, and not as 
accurate as that secured by the use of new 
cams. 

While the tension of the spring of an auto¬ 
matic valve is sometimes controlled by a nut, 
its adjustment usually depends on the 
stretching of the spring to strengthen it, or 
the cutting off of part of a turn to weaken it. 
The tension should be adjusted, one cylinder 
at a time, until the best results from each 
are secured. 


MAINTENANCE, CONSTRUCTION 307 


LINING UP THE WHEELS 

When the car is moving forward on a 
straight line the wheels should be parallel in 
so far as their forward direction is concerned. 
In a far greater number of cases than is real¬ 
ized that is not the condition, with the re¬ 
sult that the wheels will be making an angle 
with the line in which the car is moving. In 
consequence, the tires will be subjected to a 
dragging action in addition to their rolling 
movement, which will wear the outer casings 
far more rapidly than is justified by the dis¬ 
tance traveled. 

The casings of the rear wheels are usually 
slightly rough, due to the slight but frequent 
slipping caused by the quick application of 
power or of the brakes, and also due to some 
extent to the action of the springs. The front 
wheels, on the contrary, should have a rolling 
motion, and the surfaces of the casings 
should always be smooth. If they are rough 
it indicates that the wheels are out of true. 


308 MOTOR CAR PRINCIPLES 


If the car is to be kept in thoroughly good 
condition, the lining up of the wheels should 
be checked at monthly intervals. The ap¬ 
paratus required is simple, consisting of two 
stout sticks seven feet long and two pieces 
of cord longer than the car. 

Each stick is to have two notches cut in it 
near its ends, the distance between the 
notches being a few inches greater than the 
length of the rear axle. The distances be¬ 
tween the notches on the two sticks should be 
identical. The two pieces of cord are then 
to be tied to the sticks at the notches. Two 
chairs should now be placed, one in front of 
the car and one behind it, with their backs 

toward the car, and the sticks laid on the 

\ 

seats of the chairs with the cords drawn taut. 
The two strings will then be parallel at ap¬ 
proximately the height of the axles. By 
moving the chairs slightly the strings may be 
brought parallel to the frame of the car, 
and when once in position should not be 
moved. 


MAINTENANCE, CONSTRUCTION 309 

Measurements should then be made from 
the string to the felloe of one of the rear 
wheels, and if the position of the wheel is 
true, the distance from the string to the part 
of the felloe in front of the hub should be 
equal to the distance from the string to the 
part of the felloe behind the hub. A similar 
measurement should then be made to the 
other rear wheel to ascertain its position. If 
the axle housing is rigid, the relation of each 
wheel to its string will be identical, for an 
axle housing in good condition will hold the 
wheels parallel. 

If through the sagging of a spring, the 
slipping of a spring clip, or through a mis- 
adjustment, the rear axle is out of true, this 
fact will be indicated by measurements that 
will show the rear wheels to be out of paral¬ 
lel with the strings. The defect should be 
corrected. 

With the rear wheels running true, the 
steering gear should be worked to bring one 
front wheel parallel to its string, the meas- 


310 MOTOR CAR PRINCIPLES 


urement being made to the felloe at points 
in front of and behind the axle. With the 
wheel in that position the position of the re¬ 
maining front wheel should be measured, and 
if it is not parallel to its string, as is fre¬ 
quently the case, the reason for this should 
be determined. It may be due to the bend¬ 
ing of the drag link or of the front axle, or 
one of the steering knuckles may be bent. 
The drag link is usually provided with an 
adjustment, and by screwing or unscrewing 
it the wheels may be made parallel. 

The operation of checking up the lining of 
the wheels requires only a few minutes’ time, 
and the saving in the wear of tires makes it 
well worth while to perform the operation 
frequently. 


CHAPTER XVII 


CAUSES OF TROUBLE 


P RACTICE and experience are the best 
instructors in keeping the car run¬ 
ning, and the operator quickly ac¬ 
quires the ability to recognize the source of 
trouble from the action of the engine in fail¬ 
ing to deliver power, or from the manner in 
which it stops. Each part of the mechanism 
may be counted on to give trouble, and the 
possibilities are numerous, but in general it 

i 

may be said that an interference with the 
proper operation of the engine may be laid ■ 
to the failure of the ignition system or gaso¬ 
line supply, a defect of the combustion space 
in not retaining the pressure, or the overheat¬ 
ing of the engine. 


PRESSURE GASOLINE FEED 

In order to retain the necessary pressure, 
the tank and its connections should be tight. 

311 


312 MOTOR CAR PRINCIPLES 


The cap of the tank should be provided with 
a proper gasket, and should be kept screwed 
up tight. If there is a leak in one of the 
joints of the pressure pipe or the gasoline 
pipe, it should he unscrewed to ascertain if 
the parts are in good condition. In reassem¬ 
bling the parts, the threads should be coated 
with shellac to prevent them from un¬ 
screwing. 

GRAVITY GASOLINE FEED 

The cap of the tank will have a small hole 
drilled through it to permit the entrance of 
air to the tank to occupy the space left by the 
flow of gasoline to the carburetor. If this 
hole is clogged, the entrance of air will be 
prevented and the tank will become air- 
bound. 

A condition of this sort is deceptive, for 
it gives the same indication as an empty 
gasoline tank. When the tank cap is un¬ 
screwed air is admitted, and the engine will 
run until the tank again becomes air-bound. 


CAUSES OF TROUBLE 


313 


The remedy is to clean out the dirt or to pro¬ 
vide a small hole for the entrance of air if 
one is not provided. 

The gasoline line should invariably be fit¬ 
ted with a strainer which will remove parti¬ 
cles of dirt and will separate the water. The 
drain cock of the strainer should be opened 
for a few minutes every three or four days 
to let out the impurities. 

CARBURETOR 

The principal trouble given by a car¬ 
buretor will be due to dirt, which will lodge 
in the float valve and cause flooding, or will 
clog the spray nozzle. 

It occasionally happens that a metal float 
becomes leaky or a cork float becomes soggy 
with gasoline; in either case the float by be¬ 
coming too heavy will cause flooding. A 
leaky metal float should be held under hot 
water to vaporize the gasoline; the leak, 
which will be shown by the escaping gas 
bubbles, should be marked, and when the 


314 MOTOR CAR PRINCIPLES 


float is empty should be closed by a tiny drop 
of solder. 

A soggy cork float should be dried out in 
an oven and then coated with shellac. 

An instruction book covering the type of 
carburetor used should be secured from the 
manufacturers. 

MAGNETO 

The most usual trouble with a magneto is 
due to dirt, which will interfere with the cir¬ 
cuit breaker. The platinum points should be 
kept clean and free from oil in order to oper¬ 
ate properly. The lever should also be free 
on its pivot. 

An instruction book explaining the use of 
the magneto should be secured from the man¬ 
ufacturers, and it will be found to contain 
full directions for the care of the instrument, 
as well as directions for the location of 
trouble. 


CAUSES OF TROUBLE 


315 


DRY CELLS 

Dry cells should be kept in a tight box and 
protected from dirt and dampness. If their 
pasteboard jackets become wet they will 
form conductors between adjoining cells and 
cause a waste of current. Oily, dirty or 
loose terminals may prevent the current from 
passing to the circuit. 

A dry cell will give its most intense cur¬ 
rent when it is new, ( and will waste away 
with age even if it is not being used; when 
buying cells, fresh ones should always be 
insisted upon. When a dry cell has been in 
use for some time it becomes exhausted; it 
will give a current when the switch is first 
thrown on, but will quickly fail. An ex¬ 
hausted cell is useless and should be re¬ 
placed. When a dry cell is chilled it will not 
give as intense a current as when it is 
warm. If the cells do not give sufficient cur¬ 
rent to operate the motor it should be noted, 
first, that there are enough cells connected 


316 MOTOR CAR PRINCIPLES 


in series to give the required voltage; sec¬ 
ond, that the connections between the cells 
are properly made; and, third, that the ter¬ 
minals are clean and tight. 

STORAGE CELLS 

A storage cell should be kept thoroughly 
charged, even though it may not be in use. 
A good voltmeter should be provided, and 
when the voltage of the battery drops to 1.8 
volts a cell or less, the battery should be re¬ 
charged without loss of time. 

VIBRATOR COIL 

A vibrator coil will give trouble through 
the platinum points of the vibrator being 
dirty or worn, or the vibrator blade being 
out of adjustment or loose. 

The blade should be adjusted to make the 
engine operate properly with as little spark¬ 
ing as possible at the vibrator platinum 
points. If the sparking is intense at the 


CAUSES OF TROUBLE 


317 


points, they should be cleaned and smoothed 
with a very fine flat file. If the sparking con¬ 
tinues in spite of changes in adjustment, and 
the engine cannot be made to run properly, 
it indicates an internal defect that will re¬ 
quire the coil to be returned to the manufac¬ 
turer. 

SPARK PLUGS 

A spark plug will give trouble through 
the insulation becoming fouled with carbon 
deposit. The plug may be cleaned by the 
use of gasoline and a stiff brush. The spark 
plug points should form a gap of not less 
than -fo and not greater than fa inch. The 
gap may be adjusted by bending the elec¬ 
trodes. Porcelain or mica insulation will 
crack or become leaky with use, and if the 
plug is of a type that is screwed together, 
the loosening of the parts will cause a leak¬ 
age of compression. 

If spark plug trouble develops on the road, 
the quick remedy is to replace the defective 
plug with a perfect one. 


318 MOTOR CAR PRINCIPLES 


. CABLES 

The insulation of the cables should be suf¬ 
ficiently perfect to retain the ignition cur¬ 
rent. The engine should be occasionally run 
in the dark, which will make visible any 
leakage of current. All terminals should be 
tight. 


SWITCH 

A defective switch may cut out the current 
entirely, or may cause an intermittent inter¬ 
ruption of the current due to the vibration of 
loose switch parts. 


TIMER 

Irregular firing will be caused if the timer 
is dirty or packed with grease that is too 
thick, or if the timer spring is weak. A loose 
timer connection or a timer that is loose on 
its shaft will also cause misfiring. 


CAUSES OF TROUBLE 


319 


COMPRESSION 

If the engine does not develop power the 
trouble will frequently he found to be a loss 
of compression in one or more cylinders, and 
this fault may also cause misfiring. 

Compression will find an opportunity to 
leak through a worn valve or because of 
weak valve springs. Leaks may also occur 
through the spark plug parts being loose, or 
through the plug itself not being tightly 
screwed into the cylinder. The pet-cock may 
be loose, the piston rings and cylinder walls 
may be worn or scratched, or the piston rings 
may be broken. 


CHAPTER XVIII 


EFFECTS OF TROUBLE 


T HERE is a reason for every trouble 
that develops in the operation of 
the car, and as a general thing this 
reason may be determined by observation. 
The cause of improper operation cannot be 
determined by guessing at it; if the action of 
the mechanism is understood there is no dif¬ 
ficulty in locating a fault by a study of the 
effects. 

In locating engine trouble it should be re¬ 
membered that the engine cannot help but 
run if it receives a proper charge of mix¬ 
ture and if the mixture is compressed and 
ignited properly; provided of course that the 
bearings are not too tight, the crank shaft 
is not broken or some other vital part is not 
defective. 


320 


EFFECTS OF TROUBLE 


321 


The most usual causes of defective opera¬ 
tion are as follows: 

Engine will not start 

No ignition. 

No carburetion. 

No compression. 

Engine starts, but will not continue running 

Insufficient flow of gasoline to the carbure¬ 
tor. 

Dirt in carburetor. 

Exhausted battery. 

Explosions stop abruptly 

Broken wire. 

Loose terminal. 

Explosions weaken and stop 

No gasoline. 

Exhausted battery. 

Slipping of magneto or timer drive. 


322 MOTOR CAR PRINCIPLES 


Steady miss in one cylinder 

Defective spark plug. 

Stuck or broken valve or valve spring. 
Broken wire controlling that cylinder. 

Occasional miss in one cylinder 

Defective spark plug. 

Stuck valve or broken valve spring. 

Loose connection of wire controlling that 
cylinder. 

Water in cylinder. 

Occasional miss in all cylinders 

Dirt or water in gasoline. 

Loss of ignition. 

Engine does not develop full power 

Weak compression. 

Piston or bearings too tight. 

Insufficient lubrication. 

Defective cooling. 

Ignition out of time. 

Poor mixture. 


EFFECTS OF TROUBLE 323 


Slipping clutch. 

Tight brakes or transmission bearings. 

Engine overheats 

Too much running on low gear. 

Spark retarded too much. 

Insufficient lubrication. 

Defective cooling. 

* ‘ Popping * ’ in carburetor 

Mixture too weak. 

Inlet valve worn or stuck. 

Knocks and pounds 

$ 

Ignition too early. 

Loose bearings. 

Loose cylinder. 

Loose fly wheel. 

Engine base loose on frame. 

Hissing 

Compression leaks. 

Leaky inlet or exhaust pipe. 


324 MOTOR CAR PRINCIPLES 


Engine kicks back on starting 

Ignition too early. 

Engine will not stop 

Heavy carbon deposit in cylinder. 

Spark ping electrodes so thin that they 
glow and ignite the charge. 

Muffler explosions 

The result of a missing explosion and the 
ignition of the fresh charge in the muffler. 

Black smoke at exhaust 

Mixture too rich. 

White or blue smoke at exhaust 


Too much oil. 


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INDEX 


A 

Accumulator. See storage 
cell 

Action of dry cell, 163 
of storage cell, 168 
Air cooling, 44 
Air valve, auxiliary, 67 
Alternating current, 200 
Ampere, 99 
Armature, 107 
Atwater-Kent ignition, 183 
Auxiliary air valve, 67 
Axle, dead, 258 
front, 275 
live, 252 

B 

Balance of engines, 48 
Battery, trouble with, 315 
Battery connections, 165 
Battery system, parts of, 
169 

Bevel gear drive, 249 
Bevel gears, 247 
Bosch battery system, 170 
Bosch dual coil, 193 
Bosch dual magneto, 189 


Bosch duplex magneto, 
195 

Bosch magneto principles, 
130 

Bosch magneto, type DU, 
130 

types D and DR, 136 
type ZR, 138 
Brake equalizer, 281 
Brakes, types of, 276 

C 

Cable terminals, 214 
Cables, ignition, require¬ 
ments of, 211 
static charge on, 212 
trouble with, 318 
Cam, 29 
Cam shaft, 30 
Carbon deposit, 40 
Carburetion, 62 
Carburetor, adjustment of, 
301 

compensating, 69 
necessity for, 62 
trouble with, 313 
Carburetor parts, 64 


329 





330 


INDEX 


Carburetor principles, 63 
Carburetors, types of, 70 
Chain drive, 256 
Chains, care of, 294 
Change-speed gear, 223 
planetary, 240 
progressive, 226 
selective, 232 
use of, 237 
Check valve, 83 
Circuit breaker, action of, 
117 

Circuit, grounded, 119 
Clearance, 19 
Clutch, friction cone, 21 
internal expanding, 223 
multiple disk, 219 
necessity for, 216 
reversed cone, 218 
use of, 237 
Coil, Bosch dual, 193 
induction, 147 
vibrator, trouble with, 
316 

Commutator, 200 
Compression, effect of, 11 
trouble with, 319 
Compression - combustion 
stroke, 10 
Conductors, 95 
Cone clutch, 217 
reversed, 218 
Connecting rod, 25 


Connections of battery, 
165 

Cooling system, necessity 
for, 40 

Coupling, magneto, 214 
Crank shafts, 22 
Current, alternating, 200 
direct, 200 
Cycle, 5 
events of, 6 

D 

Dead axle, 258 
Delco ignition system, 183 
Differential, 258 
Direct current, 200 
Direct drive, 229 
Disk clutch, 219 
Distance rod, 287 
Distributor, 116 
Double ignition system, 
186 

Drag link, 269 
Drive chain, 256 
direct, 229 
final, 247 
shaft, 250 

Driving gear ratio, 266 
Dry cell, action of, 163 
Dual ignition, 188 
Dual magneto, Bosch, 189 



INDEX 


331 


Duplex magneto, Bosch, 
195 

E 

Electrical measurements, 
99 

Electricity, principles of, 
93 

Engine, care of, 293 
four-cylinder, 54 
horizontal opposed, 49 
six cylinder, 56 
three-cylinder, 56 
two-cycle, 58 
two-cylinder vertical, 49 
Engine balance, 48 
Engine troubles, 320 
Exhaust stroke, 18 
Expanding clutch, 223 
Expansion, 1 
Extra air valve, 67 


Feed of gasoline, 80 
Final drive, 247 
Firing order, 56 
Fixed ignition, 92 
Floating axle, 252 
Fly-wheel, necessity for, 7 
Four-cycle principle, 6 
Four-cylinder engine, 54 
Front axle, 275 


G 

Gap, spark plug, 207 
Gas engine, principle of, 3 
Gas engines, classes of, 6 
Gasoline feed, 80 
trouble with, 311 
Gasoline strainer, 85 
Gears, bevel, 247 
principle of, 31 
Gravity circulation, 43 
Gravity feed, 80 
Grinding valves, 295 
Grounded circuit, 119 

H 

Heat, effect of, 1 
Horizontal opposed en¬ 
gine, 49 

I 

Ignition, Atwater - Kent, 
183 

battery, 169 
Delco, 183 
double, 186 
dual, 188 

electric, principle of, 93 
fixed, 92 
multi-point, 142 
point of, 12 
requirements of, 86 



332 


INDEX 


Ignition cables, require¬ 
ments of, 211 
Induction, 103 
Induction coil, 147 
Inductor magneto, 157 
Inlet stroke, 9 
Insulators, 96 
Interrupter, action of, 117 

J 

Jack shaft, 256 
Joint, universal, 250 

K 

Knight engine, 34 

L 

L-head cylinder, 33 
Lining up the running- 
gear, 307 
Live axle, 252 
Location of spark plug, 
207 

Lubrication, 45 
Lubrication table, 325 

M 

Magnetic principles, 100 
Magneto, Bosch dual, 189 


Bosch duplex, 195 
Bosch, type DU, 130 
Bosch, type ZR, 138 
Bosch, types D and DR, 
136 

inductor, 157 
principles of Bosch, 
130 

Remy, 155 
Remy dual, 195 
Splitdorf, 149 
Splitdorf dual, 195 
transformer or step-up, 
147 

trouble with, 314 
true high tension, 125 
two-spark, 142 
Magneto coupling, 214 
Magneto principles, 107 
Magneto speed, 113 
Magneto timing, 141 
Magneto types, 124 
Master vibrator, 181 
Muffler, necessity for, 38 
Multiple disk clutch, 219 
Multiple-series connec¬ 
tions, 166 

Multi-point ignition, 142 
O 

Oiling system, 45 
Oiling table, 325 




INDEX 333 


P 

Piston and piston rings, 26 
Planetary change-s peed 
gear, 240 

Pole shoes, extended, 113 
Power, development of, 20 
Power stroke, 16 
Pressure, source of, 1 
Pressure feed, 81 
Principle of gas engine, 3 
of gears, 31 

Principles of Bosch mag¬ 
neto, 130 
of carburetor, 63 
of electric ignition, 93 
of electricity, 93 
of magnetism, 100 
of magneto, 107 
of Remy magneto, 155 
of Splitdorf magneto, 
149 

of two- and four-cycle, 6 
Progressive change-speed 
gear, 226 

R 

Radiator, 40 
Radius rod, 287 
Ratio, driving gear, 266 
Relief valve, 83 
Remy dual magneto, 195 


Remy magneto principles, 
155 

Rod, radius, or distance, 
287 

Running gear, to line up, 
307 

S 

Safety spark gap, neces¬ 
sity for, 133 
Scavenging stroke, 18 
Selective change speed- 
gear, 232 

Series connection, 165 
Series-multiple connec¬ 
tions, 166 
Setting valves, 303 
Shaft, jack, 256 
Shaft drive, 249 
Shock absorbers, 286 
Silent Knight engine, 34 
Six-cylinder engine, 56 
Skidding, prevention of, 
284 

Sleeve valves, 34 
Sliding gear, 226 
Spark, advance and retard¬ 
ation of, 14 
Spark coil, 147 
Spark plug, 203 
Spark plug gap, 207 
Spark plug location, 207 





334 


INDEX 


Spark plugs, trouble with, 
317 

Speed, effect of, on car¬ 
buretor, 66 
Speed gear, 223 
Splitdorf dual magneto, 
195 

Splitdorf magneto princi¬ 
ples, 149 
Springs, 285 
Springs, care of, 298 
Starting the car, 237 
Static charge on cables, 
212 

Steatite, 205 

Steering, principles of, 268 
Steering gear, 273 
care of, 297 
Step-up magneto, 147 
Storage cell, action of, 168 
Strainer for gasoline, 85 
Stroke, 5 
Suction stroke, 9 
Switch, trouble with, 318 

p 

T 

T-head cylinder, 33 
Terminals, cable, 214 
Thermo-syphon circulation, 
43 

Three-cylinder engine, 56 
Timer, 169 


Timer (continued) 
trouble with, 318 
Timer-distributor, Bosch, 
170 

Timing the magneto, 141 
Timing valves, 303 
Tires, care of, 291 
pneumatic, action of, 282 
requirements of, 282 
Torsion rod, 254 
Transformer magneto, 147 
Transmission, parts of, 
216 

Two-cycle engine, 58 
Two-cycle principle, 6 
Two-spark magneto, 142 

U 

Universal joint, 250 

V 

Valve, parts of, 27 
Valve grinding, 295 
Valve setting, 303 
Valveless engine, 34 
Valves, arrangements of, 
32 

opening and closing of, 
10 

operation of, 28 
Vibration, causes of, 48 




INDEX 


335 


Vibrator, 172 
master, 181 

Vibrator coil, trouble with, 
316 

Vibrator coil ignition, 174 
Vibrator spark, effect of, 
172 

Vibrators, adjustment of, 
300 


Volt, 99 

W 

Washing the car, 290 
Water cooling, 40 
Wheels, lining up, 307 
Working stroke, 16 
Wrist pin, 26 



* 








X 


MAR i? 1313 



















































































































































































































































































